Tires: Putting LT/285/75/16 tires on 7 inch rims, inch rims, steel rims

Question
At the guidance of my well meaning,trusted tire installer,I installed 285/75/16 BFG "E" tires on 7 inch steel rims. I have a 1994 F 350 SRW carrying a very heavy camper. The fronts look good but the rears seem to bulge from the weight and the lip of the rim disappears a little at the bottom into the sidewall of the tire. I know I am sacrificing handling by not having the proper 7.5 inch rims. So many guys cheat with the above combination so they don't have to buy new rims and my installer wanted to save me money. My question is, is this safe in the real world with all the weight I am carrying? Or am I playing with fire and prone to tire failure ? The rims are rated for the weight I am carrying.  
Thanks so much, Scared Bernie.

Answer
Bernie,

Using a rim that is too narrow causes the tread face to arch.  That tends to cause stability problems such as sensitivity to ruts in the road and the wind.  It also leads to the tire wearing more in the center of the tread.

It's not a "playing with fire" sort of thing, it's more a "playing with matches" sort of thing - not a good idea and lots of folks get away with it.