In reply to Tom Last:
I squeezed a small bouldering wall in to a new build garage (pretty much square, 8foot 2" wide, 8foot tall, length wasn't an issue really) so I'm sure either of the rooms will do realistically
Just be aware that the angle you plan is likely not going to be the angle you end up with, unless you're a lot more skilled at carpentry than myself and my friend (which, to be frank, wouldn't be difficult). I aimed for 35-ish, it's probably much closer to 40+.
Also is budget an issue? Larger juggy grips tend to be a lot more expensive than little crimpers. You could make your own too.
I bought the ply/grips off someone on here for mine and then built a free standing frameIt's not the largest of training walls but it does me. The grips are all generally pretty juggy with some smaller ones thrown in there for good measure.
I'm finding I can do 5 to 6 circuits of the wall on a route I set up on the plastic, and 1 to 2 on a route I've set up 'wood only'. To the left (not visible on the pic), I mounted a finger board too in the remaining space.
I don't boulder as hard as you, probably 6A on-sight and up to 6B+ and I built the wall largely as a bit of a project and something just to keep me in shape (not necessarily improve at climbing) which is why the steep angle and juggy grips do me. The finger board is there if I feel like increasing finger strength (though I do wish I'd gone Beastmaker 2000 instead of 1000).
As for design, mine is free standing and is really simple. If I can do it, pretty much anyone can. It's nice and stable (creaks a little!) though I wouldn't really like to do any massively dynamic moves on it!