Thanks guys, I was worried about taking that brace out in the swingarm, but after realising just how beefy it is (and going through 15 cutting wheels getting a chunk out) I think I'm feeling better.
I took it from the corner bends to the first center hole, and did a bit of cleanup around the welds. Still got bumps, don't want to go through the wall, but it fits a bit better.
Went with Lee's advice, chopped a nice piece of the intake out.
Making some more lightweight paper gaskets for the intake, and I might take some sandpaper to work tomorow and grind down the engine side of the intake as well, maybe take a bit off the reed valve case while I'm at it.
With what I've already done it seems like it's going to work, I will have to get a new hose hooked up, going swing by McGuckins (the everything store) tomorow and see what I can find, hose would do, but I'd rather use a bit of piping if I can find a close enough fit.
Worse comes to worse I could also take a bit off the front of the carb, I believe, but as Lee said, it was an expensive hunk of metal...