[rcecale]

Hmmmm, not a bad idea, Pat. Definitely worth considering.

I did some searching around on the John Bridge forum and there seems to be a consensus that the thinset isn't there to actually adhere the backerboard to the plywood, but rather to simply fill in the gaps and remove air pockets.

A few of the regulars there actually suggested setting a few more nails in the "gritty" areas, since the job of the jails (or screws) is to actually do the fastening of the backerboard.

Injecting some thinset would probably fill in the pockets, but perhaps fastening the floor a little more just might do the trick.

Gonna have to ponder this a bit.

Randy