Im currently designing my first homemade airbow but i have some doubts. #1. Whats the best size for the air resevoir???? 1/2 x 4 inch is ok? Or should be bigger?? #2. I read that 2219 arrows fit 7.5mm barrels , and 2317 arrows fit 8mm barrels. Any other arrow/ barrel size options??? #3. Probably the best homemade airbow valve is a ball valve triggered with rubber . But what valve is the second best??? QEV , pressure washer gun , homemade piston valve?