Snap-in clamp geometry
I am sure someone much smarter will be able to point you towards datasheets and maths equations that will tell you exactly what you could/can't do, however, I would say it depends on a few things:


Material - some materials have more give/flexibility, others have less. Depending how hot you expect the caps/surrounding components to get may also influence choices.
Wall thickness - Are you just after a 'thin walled' print, or something more solid. Thinner walls tend to be more flexible.
Reusability - are you going to snap the cap in once or twice, or thousands of times?


I would hazard a guess that about 210-220 degrees of "surrounding" would be enough.

Can you try it and see? Or do you only have one shot?