Fred,
I would use an ejector underlug for a pattern, the hole for the large latch trip roll pin is in the identical same spot on both underlug types, so it wouldn't be hard to make a template and use it to index off of for the other 2 holes.
MSP,
I think that wouldn't be too hard, I would drill several holes, then grind the area tween the holes with a dremel leaving enough material for the lifter button hole in the rear most hole which would be centered where the lifter button needs to be. Drilling a series of holes would save a lot of grinding, the underlug being soft does have some advantages in that it's easy to work with!!
Tim