What gearing are you running ???? I would suggest, since you want to stay with "stock" cylinders, get a good dune port job. You can find one for a reasonable price from reputable peaple if you look.
as far as the launch, GEARING is everything !! ALOT of factors there too ( kind of ground, sand dirt, wet, dry etc. etc.) but, to start I would probably try a 15/41 gearing, and leave in second. Thats with a dune port, Buts its all trial, and error. Everyone will tell you that.
Good luck !!!