Your right, 17.5 would be the right choice for the novice class, but like so many guys my friend likes to "BASH" his truck. And a 17.5 when bashing is, well boring.
Also money is a factor, and if he has any success he'll move up in class.
Now for me, the best class @MRCR is 17.5 non ramping short course.
For my friend it's OPEN,OPEN,OPEN!!!!! He just wants to jump everything. So a big motor is what he's looking for. If you could shoot me a price I'll let him know.