if your going to mod that valve any make sure you have one just in case , heaven forbid, it gets screwed up. then your at the mercy of the postal or UPS getting another to you, if their in stock, just so you can shoot. extra parts , springs, TP valve stems, all is nice to have on hand just in case>
valve # 1700-100 $24.84 + shipping
I dont know if opening the valve port up or adding more volume space would help any, maybe some, but also more air usage per fill.
\\\ X ////
one step closer to the ultimate goal