As my pistol instructor says "If you have to reload you better be shooting at an army" Which means if you need more then one shot then you need to practice.
Joking aside I would get the long mag and tap that, its 29 rounds of HPA death. Also do not go and drill and tap all of your mags keep at least one you can run propane on, because you never know. Also buying and tapping 7 mags would cost you close to $300 and thats the sucky kjw mags. One tanaka short mag is 60 shipped ( the cheapest I found).
Your best bet, keep a speed loader, count your shots and reload when no one is around, and when you do reload have your pistol very very close buy. I cant count the times I have gotten shot when reloading.
Also with the above method of on/off you have a very loud popping noise when you disconnect the coiled hose, to put it on the next mag.