I have recently (at the time of original posting) taken up cycling a recumbent (a now discontinued Azub Eco 20" bicycle). My perineum thanks me, but immediately after a ride I feel a bit lopsided (more than usual). I presume I'm not sitting quite straight on the bike (or the seat isn't quite straight) so I am always leaning slightly. Is there an easy way to check whether I'm correctly positioned? (Or is it just my body that's asymmetric?)
I'm not aware of a 'specific' way but I'm fairly certain that if you got the bike frame vertically level then placing a level across your seat would show you if the seat is level.
Part of the problem is that you're riding a trike, and that roads aren't flat, so you're continuously on a slight lean.
Its totally normal and to a large extent unavoidable.
You might be able to fit shims in your seat mounts to help angle the seat away from the camber of the road. The boom might be able to rotate a couple of degrees too, without causing significant problems to the chainline.