Is it legal to have your bumpers mounted on the far outsides, with no support in the middle of them to allow better clearence for wheels?
R26 states your bumpers need to be supported by material within 1/4" of your frame perimeter every 8 inches. There are no restrictions on how or where your bumpers are fastened as long as they are rigidly attached to the robot. You should be able to pick your robot up by its bumpers. If you can’t do that, they probably aren’t rigidly attached well enough.
One option is to only run corner bunkers, and then the 8" gapping doesnt matter, giving you clearance for wheels in the center.
Of course, that risks your wheels getting hit directly, and in a way that doesn’t create a foul for the opponent.
No, that is not allowed. Read the rules.