Originally Posted by Gmww
That's some nasty stuff to try and control. Might consider an epoxy filler.
I agree it is nasty. But a little at a time, and careful masking and daming with putty, etc it is manageable. My old hobby was RC planes and I used the stuff quite a bit in that context and if you are careful it is workable. And it is also reversible if need be.
Only possible drawback could be that it might compress a bit over time. But then I figure you can go the bicycle patch shim route.