never tried it before, but a 12" dry mounting press might do the trick... start at low temperatures and work you way up.... it'll warp the emulsion right off the paper of a color photo if you're not careful, so it it'll flatten the record one way or another... who knows what might happen to the sound though...
http://www.bhphotovideo.com/c/product/46574-REG/Seal_Bienfang_SE168_110S_Swingarm_Dry_Mounting.htm l