[Hummer23]

No I have never altered from the stock tires pressure. Probably should try though.
As far as trailer, my snowcat trailer is all alluminum and only weighs about 500 lbs, (gotta love alluminum) so even with 2 sleds on board (600 lbs each), I am only pulling less then 2000 lbs. Now it pulls that pretty nice, in fact with one sled , I barley notice it, but I still use D3 because I think it is much better to run at a little higher rpm all the time, instead of shifting aound too much.