You may have already determined what shape your valve stem seals are in. If they leak, you might have an easy answer to your oil burning question.
I'm going to ask for correction but I think I'm right in thinking that between the rings and the valve stem seals, if your oil burn is present in a big way right at start up, it is likely that the valve stem seals are not doing their job (oil sitting on top of pistons). The other test is to shoot some heavy oil in each cylinder (via spark plug hole) and see if compression improves. Compare results between cylinders. If a big improvement is seen on one cylinder over the others, you probably found the cylinder with the problem. I say cylinder, because unless you measured the bore after the machine work was done, you might be the lucky recipient of a bad machine bore and honing - rings are fine, but the bore is too big, or not round (perhaps machine shop couldn't bore enough to make round again!)
Just some thoughts.