Wow! How thick are you working with? I make police service holders (maybe 1 a month) and use 10oz backs and spacers, and 8oz fronts and awl it without much trouble. I agree with the other guys, don't drill...the awled hole will close back up on the stich and hold it tight (service holsters get a lot of abuse). I used to use a stiching needle/awl that has an exposed lock stich on the back, I use the double needle method now ind it's much faster. I made my awl from a 1/8" chainsaw file I left out in the weather. Snapped off about 3", annealed it, and filed/ground a long taper on the last 1-1/2" or so to a rounded point, polished it, rehardened and tempered it and set it in a "mushroom" handle carved from scrap maple. Also made a small maul from glued and laminated maple scraps. Works fine...a tip, no matter which hole punching method you end up using, don't get more than 3 or 4 holes ahead of yourself. When stiching near an edge, like a holster, the leather seems to streach from the stress of the hole making (even when glued with barge glue, like I do during assembly), and pulling each stich tight to set it and you'll find that the holes won't line up easily out there ahead of yourself, you'll spend more time trying to line them up, especially with 3 thicknesses like a holster, or "search" with the needles trying to find a path through the piece.
I love leather work as much as I enjoy ML building.
Oh, but the way, after running out of waxed linen, I found some in the Wal-mart craft section for $2 for 75 feet, enough to do 3 holsters.
John