Moment of truth...
Hatch clears with miles to spare. Did run into some little issues though.
Since it was raining today, I couldn't bring the welder out to the truck for final positioning, so I tacked it inside and fitted it out.
May have lost just a hair of departure angle. I can resolve that by rewelding the carrier arm closer to the hatch, maybe up to an inch closer with a good gusset underneath (that's as far as I dare go given the cantilever design). The tire does look a little far away from the hatch as well, but I think the depth should be right on par for a 33". I was also going to put on some lift shackles anyway, so I'm not too worried about it.
My original measurements, even accounting for a 33" tire, were evidently way off. While the arm is placed perfectly for the spare 30.5", it needs to be moved slightly toward the center to accomodate the eventual 33".
I had to do a few other things at the shop so I didn't have as much time as I would have liked today. So, tomorrow, cutting and rewelding. Hopefully it's a nicer day so I can do it right on the truck. Then finishing and painting. I left it on the truck (coated in anti-spatter which should prevent rusting in the rain) because it just looks so right otherwise!