I still have to photo this mod, but I was digging through the Lego box and discovered some Lego tires that push about halfway onto the ZZ MT wheels, leaving a big space on the end.
Well I grabbed a Lego Wheel, and cut it down the notch with a hacksaw blade.
Now the space has a Lego wheel filler, while the larger tires get a push out to boot!
(Three more were cut to match in moments.)
The tires simply push onto the ZZMT wheels, however some of the stock wheel is left exposed.
I don't know if that will cost me points or not.

(I dunno, pretend it's a brake drum or something...)
The difference with this mod over others I've seen is that I'm not deforming the tire by pushing it on over the center ridge, but using it as a stop for both the ZZ MT wheel and the Lego wheel filler end piece.
The effect on performance is very good.
My Monster Herbie Crawler is lifted higher, and the additional weight of the Lego wheels helps when climbing.
pics when available!