One trick on hole spacing is to measure them 3 or 4 different ways then compare results. I'm overly careful amount reverse engineering parts, because it sucks making a part a dozen times to get it right. Measure, measure, measure, measure again, then one more time to be sure, when your done with all of that, check it again, especially if you generally screw it up (lol)
Don't forget to make sure you calipers are set to zero, plus it wouldn't hurt to check them on a gauge block. You'll pick up tricks as you advance, I'll give you a clue, you can use software to check your drawing against the actual part.
lol don't have that software.
its not the hole size its the placement.
ill keep working.