FWIW, on a 9" wheel. I don't think I'd run a 295 on a 10", personally, it might add some response to the car, but the tire will be more load sensitive and likely break traction easier.
A 295 has a ~10.9" tread width and a ~11.9 section width. Even with a 295/45/17 the minimum recommended rim width is 9.5". You're giving up tire wear and traction in all directions. Squeezing it down onto a too-small rim won't put the contact patch down the way it was designed, so it doesn't improve straight line traction.
I'm running 295/40/18 on an 11" rim with DrDiff 1" relocation kit.
That's the way to do it!
I run a 295/35/18 on my Duster with 18x10's. Even with those I'm at the minimum recommended width, which usually sacrifices some handling responsiveness on the tire. But going up to an 11" wide rim limits the choice of affordable rims pretty significantly.
I thought 285's on a 18x9.5 wheel would hit. Do you think it would fit since you run a 295 on a 9"?
It'll depend on the car and whether or not you want to trim your fenders. Some cars will probably be fine, others might have issues with rubbing during cornering, carrying passengers etc. It will also depend a lot of your suspension- what your ride height is, how stiff your springs are, whether you run sway bars etc. The more body roll you get the more clearance you need.
You'd be surprised how many people will tell you they have massive tires on their car, but leave out the part where the tires stick out of the quarters and how the back of the car is 3' up in the air.