I think the stock angle is a little lower in the front. This will give you the straightest stroke. The rear shock pivot does go forward and down on bump. I have mentioned previously the stroke is just going to have to be crooked because of the geometry of the standard pan car. Just don't worry about it. Rebuild the shock as needed. As far as keeping off the ground, you are just going to have to go stiffer with that center shock spring. In my test this has almost no effect on steering so just keep going stiffer (and maybe 1 mm higher) until your chassis and pod are protected. Slight wear can be accomodated on the worst bumps by changing the rearmost chassis screws once in a while. You could also sneak in some downstop limiters. It can be cushioned with an O-ring. These would be between the spring seat and the O-ring end of the shock body. I have never needed to do that.
John