That's a great tutorial. Since I'm done with NiMh and NiCd batteries, I was browsing through LiPo batteries on some RC sites and whenever I spotted one that caught my attention, I would take the measurements and reproduced them on some cardboard box, cut it to dimensions, fold it and attach it with some tape and voilĂ*! This way, I can put it into the handguard and see if it will fit and unfortunately, the smallest one would not.
This guide however might come in handy. I'm not wanting to get an airsoft branded LiPo but that specific
model that Kong Power is doing looks like the most appropriate.