Kev, he might not care about speed if he is on the sand dunes. Just having the torque of a diesel might be fun enough. If he is going to paddle it all the better.
Speed is second to just getting motion going.
I do know a standard VW with the air knocked down to 15 PSI does well on the dunes. My kids did it all the time. We also owned a 89 4WD Subaru Justy and it would kick butt without the tire pressure lowered. Man would we get the looks from the monster trucks on the beach when four of us would pile out of that little tin box.
idk why it took me this long to see this...
but for the sand, you dont need torque, you need POWER..
sure, paddles work great, but they dont work unless you can SPIN THE HELL out of them..
our aluminum rail has a 327 chev in it.. safely spins 10k rpms.. seen it bury an 8k autometer tach plenty of times.. this engine has been alive for 30+ years.. well, its about 500hp, and like 200 ft lbs torque..
paddle tires need power to float on the sand.. if you have limited power, but lots of torque, i just dont think it would work good..
you need power in the sand.. look at all the buggies that go the best.. they have LOADS of power..
vehicles with less than adequate power just sink.. they cant spin the tires fast enough to get on top of the sand.. sand is much like water.. you need to get on plane.
and im not just saying this to say it.. ive spent a good portion of my life on the oregon coast dunes with different quads, bikes, and rails.. the first rail i ever drove was my dads fugitive framed VW powered rail.. had a BUILT 1835cc a/c engine, dual WEBs, and a fatty header.. that thing was damn fun. but it had power too.. ive seen plenty of baja bugs, and rails with stock, low power a/c engines, and they just dont go good. the ones with no power also beat you more.. you feel every bump rather than just skipping across the high points..
i should post up some pics of the rail one of these days.. a couple of you guys would poop..