rim width and mfg. recommendation

Evening from a cold No. Michigan,

Looking at the possibility of an Austone for the drive tire for my 2005 HD Electra-Glide with a Trans-Moto hack. First tire was a Dunlop Elite and ran 6000 mi before cords showed. This year a Shinko 777 went a miserable 2200 miles before blowing out.  

Now, the Austone tire is recommended for a 5-5 1/2 wide rim. The rim for the bike (running with a MU-85 16) measures at 3.
Seems to me that this could cause a problem with proper tire/rim mating. This especially with the added lateral and diagonal tire forces generated with a sidecar rig.

I would appreciate hearing from another hack rider with road experience with the Electra-Glide and a Darkside Tire particularly the Austone.

Thanks for reading,
Ed