Great info there Simon - timely for me, also, as my GR1 kit is coming to me, and the only holes I wanted on the top of my Gretsch copy (apart from the f holes), were the bridge post holes, cos I figured, they'd get them right! Maybe I should have asked for no holes?!
I was toying with the idea of using a rosewood, or ebony jazz style bridge, which I still could do, if the holes are indeed off on mine.
I actually bought one of those schaller adjustable roller bridges, because the pickups I'm going to use have really wide pole piece spacing - 56.5mm at the bridge, now, I wonder if the post holes are correct diameter, also...
I should have researched more - rolls eyes...
The Schaller roller bridges come as standard with posts with M5 threads that are too small for the kit (and a lot of other) post inserts, which have M8 threads. But Schaller do sell M8 posts for the bridge separately. I’ve got a roller bridge and the posts on order direct from Schaller to try out on my ES-3 to try and cure my bridge buzzing issues. It is about the lowest height bridge you can get, and it should end up as low as my modified Nashville if I’ve measured correctly, and I can sort out any string spacing issues at the same time. The gold plated version isn’t cheap though, almost as much as the kit cost, so it better solve my bridge problems!
The different kits have different issues. The Gretsch ones seem to be OK with regards to neck angle and bridge hole positions for the builds I’ve read about, so hopefully you’ll be OK. Two-piece floating bridges are normally taller than tune-o-matics, but being wood, they are a lot easier to modify and lower if necessary, though there are limits. as to how much you can take off before the bridge becomes too flimsy or flexible.