Allowable stretch on front runners

[fissionspeed]

Hi all, I've gotten ahold of some M/T front runners to use on my car. The spec M/T lists for mounting them is a max 4 inch wide rim. However, the shop local to me (and comes well recommended on the forum) only carries minimum 5 inch wide barrels. Does anyone run this type of tire slightly stretched? Or should I pony up shipping for the 4 inch wides?

[Stainless1]

Are these the 17 inch or the 15's.   I would say stick with MT, they made the tires.  When they spin fast, the tire will grow in size and try to pull off the bead... if the rim is too wide it might make it easier. 
 

[fissionspeed]

Are these the 17 inch or the 15's.   I would say stick with MT, they made the tires.  When they spin fast, the tire will grow in size and try to pull off the bead... if the rim is too wide it might make it easier. 
 

This is the 15 inch, 27.5 height

[kiwi belly tank]

Is a 15" donut spare rim an option for you?
I'm not ashamed to shop in the racing section of a junkyard.
  Sid.

[jimmy six]

I have different center pattern space save spare 15" rims. There are some at 3-1/2" but most are 4". Many have a negative offset which is fine for me. There are a few "high dollar" cars with welded forged aluminum ones.