If it's possible, triple that flow rate. Most have found a direct co-relationship between rate of flow, and speed of abort. My aborts run 6-8 minutes using a demand valve. Many who said oxygen didn't work at all at 10-15 LPM, found aborts in less then 10 minutes by ratcheting the flow up into the 25-40 LPM rate.
I stole the following from a Batch Post...his posts are very long and sometimes technical, read them anyways,

He is our board guru in the oxygen world:
I also prefer breathing straight from the green "T" manifold on the O2PTIMASK™ or the 22 mm coupler on the demand valve. This provides the least flow resistance and minimizes re-breathing the residual volume of exhaled breath in the "T" manifold that contains highest concentration of CO2... This is important as CO2 stimulates vasodilation and slight elevation in arterial CO2 levels can occur even when breathing 100% oxygen at 15 liters/minute due to inadequate lung ventilation. That will result in longer abort times as CO2 is a more powerful vasodilator than 100% oxygen is as a vasoconstrictor.
The most effective method of pumping CO2 from the lungs is hyperventilation and the best way to do this is by using the breathing technique that starts with exhaling at forced vital capacity tidal volumes. You do this by exhaling forcefully with jaw dropped until it feels like the lungs are empty... They're not... Without hesitating, do an abdominal crunch like in doing sit-ups and squeeze the chest chest muscles then hold the squeeze until your exhaled breath makes a wheezing sound for a couple seconds. This will squeeze out another half to a full liter of exhaled breath. As this last volume of breath you exhale, the end tidal flow, contains the highest concentration of CO2, you'll be pumping CO2 from your lungs as effectively as possible.
After a couple seconds of wheezing, inhale rapidly without any delay until it feels like your lungs can't possibly hold any more then repeat the forced exhalation without delay. Keep repeating this sequence as rapidly as possible until the abort. As you're ventilating the lungs more than needed with this procedure and breathing technique... you're hyperventilating.
Try this with room air. If you're executing this procedure and breathing technique properly you should start feeling the symptoms of paresthesia after three to four complete breaths.
The symptoms of paresthesia are an important indicator that you're hyperventilating effectively. They include a very slight tingling or prickling of the fingertips, lips, or back of the neck. You'll also experience a slight dizziness or feel a little woozy. As strange as this may sound these are good symptoms and the best indication you'll get the fastest abort possible. Remember what they feel like. If you don't experience them during oxygen therapy... you're not breathing correctly... and your abort will take longer.
This method of oxygen therapy is hard work. You're forcing yourself to breathe at a faster rate and at a greater tidal volume of breath than your body's normal respiratory control mechanism is signaling. If you're doing it properly, you will get tired.
Accordingly, a high-flow oxygen regulator good for flow rates up to 40 liters/minute or a demand valve make this method of oxygen therapy possible.Tips and Fine Tuning... I've found that exhaling away from the green "T" manifold on the O2PTIMASK™ in stead of through it and out the exhaust flapper valve eliminates re-breathing the small volume of exhaled breath in the "T" manifold highest in CO2. I press the open end of the "T" manifold lightly against my lower lip while exhaling to block any loss of oxygen while the reservoir bag fills.
Starting oxygen therapy early at the first sign of an approaching attack is best... That includes shadows... A shadow is just another cluster headache. If the CH wakes you from sleep, get on the oxygen ASAP!... You're already behind the problem and any delay will only add more time to the abort.
Data we collected during a study of this method of oxygen therapy we conducted 2007-2008 revealed a simple fact many of you already know... After analyzing the results of 366 aborts with this method of oxygen therapy, we found the higher the CH pain level, the longer the abort times.
We also found the relationship between abort times and CH pain levels was linear up to pain level 6 on the 10-Point headache pain scale. In other words a KIP-3 took an average of 3 minutes to abort, a KIP-4, 4 minutes and so on up to KIP-6.
At pain levels above KIP 6, the relationship between pain levels and abort times becomes exponential. For example, a KIP-7 took an average of 8 minutes to abort, a KIP-8 took 9.5 minutes, and a KIP-9 took an average of 12 minutes.
Keeping the oxygen cylinders stored in a cool location helps as well. This is also an area where the demand valve has an advantage... The rapid expansion of compressed oxygen as it expands from 120 psi (8 BAR) to ambient that takes place within a demand valve cools the oxygen flow considerably. I've measured the temperature of the oxygen cylinder and then the temperature of the oxygen coming from the demand valve with the purge button pressed and came up with the following. The purge valve is rated at 40 liters/minute... The temperature of the oxygen cylinder was 70º F and the temperature of the oxygen coming from the demand valve was 42º F.
I also measured the temperature of the oxygen coming from my O2PTIMASK™ at a flow rate of 40 liters/minute selected on the Flotec InGage™ oxygen regulator and it was 65º F. This resulting temperature is due to the regulator on the oxygen cylinder absorbing some of the chill from the expanding oxygen and thermal gain as the oxygen travels through the oxygen tubing. Clearly the shorter the tubing down to 3 meters, the better.
I warned you it would be long, and that's only half his original post! But you begin to see how critical the higher flow rate is to speed the abort and help you dump the other treatments for aborts.
Joe