I would drill as many holes as you can do in 1 setup, then indicate in off of the existing holes. Depending on how many times you have to do this, there are 2 ways I can think of:
1- Just use an indicator in the 'last' hole to 'indicate' then move to the furthest away and try to tap that in. Go back and forth until you get it right. You can indicate in with a coax indicator, last-word style indicator, etc.
2- To be most accurate, you need to again do #1, BUUUT to make your life way easier: Clamp piece of material down to the table, face it, then clamp down your piece on top of the plate. Drill/ream the 1st bunch of holes, going through the plate below (hopefully lined up over your T slots
). Keep the plate attached, but remove the piece. Put gauge pins into a few of the holes, and use THAT to align the piece on the same 'line'. That way you don't even have to move your DRO, since you'll just be 'redrilling' the last few holes.