I have one of those cylinders, it doesn't have a predrilled hole in it though. Not sure if that hole is original to the cylinder or not, but I don't think it is. I could be wrong. Thanks for posting, I'd been looking forward to the next installment of this build.
Nicholson 500x (Project)
Nicholson 185s
Nicholson 110 (That takes an atc70 tank)
Ascott 500 head/350x (Project)
Homebuilt Racer Chromoly Suspension 110 (Ragin Runt)
PK Racing Suspension 70
A+ Inc Suspension 70
AWS Aluminum 90 frame
Hi Performance ATC Suspension frame rd350
Hi Performance ATC Suspension frame 90