fits in El Vigilante airgun?
Yes, it should
is it designed to withstand the recoil of a spring piston air rifle?
That would be a question for Centerpoint, I wouldn't think so though
Why Don't you have an ON/Off switch for the Red Dot sight.
The rheostat functions as the on/off
What's the mount 11mm ? Weaver? How come nearly zero of the products indicate the rail size they mount to?
This is a weaver mount same as picatinny they are considered the same. Second question unknown? You could call and ask?