Picked up the Fab Defense SAD-58 polymer handguard set.  The lower went on just fine but the upper is a mofo.  Cant get the heat shield to marry up with it.  I've read a few people said it was a tight fit & some shaving was required.  I did try to sand it down a but but no luck.  Any tips or suggestions are appreciated.  Thanks  ;)

I found the upper is very tight. It rotates onto the guard, then stops unless you use a large flat screwdriver to hold the guard. Once installed, it is solid.

I noticed that once installed, mine warped the upper Guard, and caused some contact between the rod-guide tab and the gas-port end of the rod. I adjusted this by sanding down the tab.

I also read before installation that people had problems with the Picattiny rail sections, so I did not use them. I believe they would also contact the gas tube or rod.

I had to tap on my lower with a rubber mallet. The upper I had to remove material at both ends with a file for the heat shield to fit.