I don't see how a rock crawling game could ever make it. The only way to get the adrenalin rush from the slow rock crawling is to risk hurting your nice rig, breaking parts or from rolling over and hurting yourself or others. Kind of hard to put that slow-motion risk/danger into a video game.
Also it is not as hard if you can see under your rig as you drive.
screamer4x4 is temperamental as hell. i was pushing my luck using it on my 4 year old PC.. had to turn the graphics down bc it doesnt play nice w new video cards. havent played it in over a year.