IMO, if you build the motor you just listed, the decision is already made to run a long swingarm. Override, alky, hp expected, all lead to a hillshooter/drag setup. Yes you can still dune as I do mine (70+ hp) but it not like your bangin berms out there. I run a +10 but on a trike, quad has much more front end weigh so the +8 may be the ticket. I wouldn't go any shorter, or your leaving untapped power on the table!!