To fit an accu-wedge, shave the bottom of the lower portion bit by bit until you get the extra tension you're looking for. Generally that leaves very little material on that bottom portion, but it can be done. Steve/RRA
I spoke with someone who used an earplug to take the slack out between the lower and upper receiver. He used a yellow cylindrical ear plug made by EAR. It seemed to work alright and it was not too expensive.