Interesting link on the air cylinder. Let us know how it works!

FWIW, I'm using a 3" peep hole on the bottom of my bell. My bell is 1/4" thick at its smallest thickness and is hydroformed steel, so YMMV. I think you'll be fine cutting a view hole (or two) as long as you bore between stiffening ribs. See what you can see through the stock openings for the clutch fork or perhaps the front dust shield, the drill as necessary, if necessary.

Randii