You have to first disassemble the back pack, then i put some red paint on the pegs on the FAST pack boosters, dont let it dry then hold them up to the back pack to get the size and location of the holes correct once thats done you can wipe the paint off the peg and let the paint dry on the backpack then cut of the holes. One thing when your cleaning up the hole with a file you'll have to file at an angle so the boosters sit properly when you put it back together
Hybridchild