You don't have to tighten the bolt very much to get it to seal. I had a very small amount of grease squeeze out past the seal at first, but another 1/4-1/2 turn of the bolt took care of that. The metal assembly on the back side didn't appear to distort at all under the force.

Andy

Edit: there is enough space for the grease to get through, even if you don't push the axle through at all (the bearing/bushing isn't a press fit of course). It takes a little while for it to ooze through, but it does work. I first did mine this way until I realized I had no way of knowing how much was coming out the back, at which point I then put the spacer back there so's I could see.