[craigosh]

If you want to have them as dirt jumps jim try and use soil with a good bit of clay in, it'll hold together better and the trannys wont get to cut up.

Shape wise, probably want doubles to be rounded but that doesnt work so well when they are large so i prefer to square off the lip of the take off and round out the landing a little. Table tops i'd square off the lips otherwise they are to easy and just mounds.

Shape of the takeoffs i'd say they should be straight for the last 2 thirds of them, with the first third transitioned for a nice smooth entry. Landings the same really, but with a shallower angle and less transition to flat. Slight anti-transitioned landings are a bit easier to land on. Kickups at the lip are a bad idea really in general, they will either kick the car nose up or clip the rear and send em nose down..

It all depends Jim on how tech you want to make them.

Motorcross dimensions would work fairly well but i'd make the takeoffs a little steeper.