I have a Lade on 24"s right now and I can say it doesn't ride to bad but a hummer has stiffer off-road suspension and big rims like 24"s, 26", or even 28"s would make for a horrible ride and it would make your truck built to go off-roading with pointless. I my self like big rims but but for an H2 I don't think you can beat the look of some 22"s wrapped in Nitto Mud Grappler. Although my hummer dealer is saying that some wheel/tire packages void the factory warranty and with tires like this would I need to do a lift at all? Just thinkin ahead so I don't get an H2 and get disappointed when it comes to doin some mods.
I hope it can be done because sorry to say I have my eye on a 06 Range Rover Sport. Don't ask.
http://www.nittotire.com/tires_mudgrappler.asp