Fuckin' god damn, the drill melted the bottom of the PVC endcap as I drilled it. Then I had to sand it down for about an hour. And then I found out the drill bit I used was too small. I'll have useful numbers tomorrow. Probably.
A lesson in homemades.
1) ALWAYS make a hole in some wood and see if the valve fits through first, so you know what bit to use.
2) ALWAYS go slow when drilling, PVC tends to melt, like all other plastic.
3) Try to use a spade bit when drilling the hole for your valve, easier, and makes a better hole in my opinion.
4) Why are you still reading this?
Good luck man. Yeah, cut down your barrel, wayyyyyy too long. Tell us your numbers soon.