Hi FW. Your assessment was pretty close to being right. It is a bit of a pain trying to align the drill with each centre punched hole properly. You really have to be completely fastidious about it and it takes time. That said, it is pretty solid metal and doesn’t seem to sag with the drill, so I am putting down the tiny differences to my alignment technique. If I can get it as close on the new body though, I will be happy. There is another one I saw, which is US made and costs over $300aud..., with shipping, it would be cheaper to get a bigger drill press!
I am pretty confident with how I can do it and how it works now. I spent hours trying to work out how to clamp it (my clamps don’t reach far enough to get both sides and clamping one side introduces a slight lean) but, working methodically and carefully aligning it seems to have got the right result.