Helicopter Vents

[Doofus]

Hello,

I don't have an Ultima, but I suspect you guys will have the knowledge I need.

I bought a pair of helicopter vents (two pairs, actually, becasue I thouht they were sold singly), and they apparently require an 89mm hole.

Except that hole is too big, and now I've screwed up my side screen.

So before I have another go, I'm hoping somebody can clarify the fitting. The hole I made is the right size for the vent to be held in place by the two tiny lugs on the inside of the two ears, if that makes any sense. I can't clost the vent, because it rattles around. I am assuming that I actually need an 83mm hole, which is the outside diameter of the 'collar' between the dome and the inner lip with the ears.

If you have any idea of what I'm on about, then I reckon you'll know the answer.

Thanks

[Doofus]

What factory? As I said, it's not an Ultima.

[Doofus]

I'm happy with the size Ive bought. My question really is about how tight a fit they should be, and tight to which part of the vent.

[Doofus]

yeah, theyre about 4 or 5 mm too large, so not really suitable to be 'repaired'.

new acrylic bought; new hole saw too.

attempt 2 coming up...