I use an awl to center the holes and perhaps enlarge them just a bit. I've also noticed the pull rivets are not all the same size so where one won't fit try a couple others. They are also not perfectly round - so try to clock them to see if they fit. If after a few grabs from the rivet bucket while clocking then a bit with the awl still no joy then the #30 comes out. I've read (and it makes sense) that pull rivets won't expand and fill as well as standard rivets (they can only expand to the diameter forced by the mandrel). Using the above, you should find very few holes that need drilling. Lot's of cleco's also help.

We are doing 2 12's side by side. On the emp, hardly any enlargement was needed but a lot of the wing skins would just not go. As others say, beware of forcing the rivet, the material is thin and will push away of you are not careful. As there are 2 of us building, it was quicker to touch the holes with a new #30 bit in a lightweight electric screwdriver.

We started on July 1 and now have 2 emps, 2 tailcones and 4 wings finished. Fuselages about to go into primer before assembly but thus far, trial fits seem better than the wings.

I also agree that you do get some big LP rivets - if it doesn't go into an adjacent hole it gets set aside for last resort use.

;) That ended up being my preferred technique. It's fast, only adds 1 to the number of tools you need to use with 2 hands and minimizes the number of reamings you perform.