Hi DRG
I would look at it this way.
It doesnt matter that the Quad gave the -crew- "some measure of protection" in game terms whats important is that the vehicle -itself- doesnt have this protection. The windows, the underbelly and most importantly, the radiator arn't protected at all.
see
http://tanksww2f.chollie.co.uk/files...ord/Quad3J.jpg
Though the crew may have some protection the vehicle itself cant survive in schrapnel (let alone small arms fire). If because of nothing else other than that the radiator would be holed immediately, I doubt the engine would run for long dry. It is clearly not an armoured car.
As far as compromising goes without going into semantics the Quad is clearly 9/10ths truck and 1/10 Armoured(steeled really) car. It would seem to me that 0 is a far more reasonable option than 1.
There is no evidence that the body was desgned to deflect shell splinters.
Best Regards Chuck.