Just made up a rivet masher from a set of home depot 24" bolt cutters. The only problem is that to get the surface area needed, I had to grind the face of the cutter, as we all do, but in doing so there is not enough reach to flatten a rivet. Completly closed, it will hold a rivet tightly but will not compress it at all. I have an idea on what to do but was wondering if anyone else might spew forth from a similar experience.

Yes, I know exactly what you mean. If you look at the photo of my bolt cutter, I had welded a 1/2" thick block of steel to the one jaw so it could fully compress the rivet. Then the block had a dimple drilled into it that supports the rivet head.

Did you try adjusting the one jaw using the adjusting bolt? It's visible on the lower part of the above pic. Loosen the bottom bolt, adjust with the top and then tighten the bottom to hold the adjustment. Thats all I had to do to increase crush.

Unfortunately, mine are from home depot and don't have the adjusting screw.