I have a similar set up, including the clear plexy tube. I also drilled a small hole in the top of the tube (away from where my cock is) and use my finger to tap the hole allowing better control of the suction.
That must have been a great cum. I just love hearing your cock begging "pleeeeease....oh pleeeeeeease.....mmmmmmm.......pleeeease. and then the orgasm. Mmmmmm....Mmmmmmmm. I know what it's like when the orgasm is going to happen and there's no way to stop it.