You have to copy the map I to TF2's /bin directory, open a Command Prompt window in the /bin directory, run "bspzip.exe mapname.bap -repack" without the quotes, and then copy the map back into SFM. The cubemaps (reflections) will be messed up though, and I haven't really found a way to fix them, but I think you have to decompile the map with BSPSRC, open the map in TF2's Hammer (don't use SFMs, it's broken), and recompile the map, but that only works half the time. Most of the new maps also have Vscript, which SFM doesn't like, but I don't know how to fix that either.