I've mounted/inflated race slicks on rims the same width as the tire. Its pretty easy especially with brand new tires and rims, but you might need to use a ratcheting tie-down strap around the center of the tire to help inflate and get the bead to pop on yours.
(spraying windex on the tires bead area helps with mounting and getting the bead to pop too...)
But I dont have a tire bander (like my pic below) that are typically needed when using rims 2" wider than the tire. So I've always just had those installed/inflated at my kart shop.
Those tire banders also help keep the tire from growing/retaining a slightly larger diameter when the bead finally pops/seals at the super high air pressure levels needed.
(sometimes it takes as much as 80-100lbs. to get the bead to pop/seal)
On my oval racer, the mounted-tire circumference is very critical because we want a different/specific stagger for each of the 4 tires on the kart. This stagger technique is just done so the kart will end up turning left much better on an oval track. We want our right side tires to be quite a bit taller than the lefts. We tune the stagger-levels to best match the corners of different tracks.
Staggering the tires is done with pretty much all forms of oval-racing vehicles, but this technique is
not used when you will be wanting to turn both right and left equally well.
That works, you just gotta be really careful so you dont loose any fingers too...