I run a YS 170CDI. What I did on the 3 screws to the flange is:
I replaced them with #4-40 capscrews. I use locking #4-40 nuts and the screws are long enough that they run interference with the cylinder cooling fins and prevent the flange from rotating.
On the cap I use a tie-wrap to hold the cup down and a real thin tie-wrap to the cap itself to prevent the first tie-wrap to slide back over the bridewire and ruin it.
Rene