Crater rim reconstruction & bug in my rotation file

Good morning everyone,

I’m currently reconstructing (more like trying to) ganymedes light and dark terranes and since I am pretty new to gplates I was wondering if I can reconstruct crater rims. There is a part of one crater on either of two moving plates. Since the plates are moving away from each other over time I would like to move the respective rim part to move with its plate. I was thinking about creating two poly line features which then move with either plate or is there an easier way. Also when creating a new feature collection for craters I noticed that there is no ‘crater’ feature or is there one which resembles craters but with a different name?
My other question is regarding my rotation file and reconstruction. I reconstructed a plate further back in time and made a stepover regarding the fixed plate. I want the plate to stay in that place when reconstruction further back, but it keeps moving back to its present position over time.
600 0.0 90.0 0.0 0.0 500 ! Platte 6 Perrine Regio end
600 100.0 0.1002 -62.9111 1.3054 500 ! Stepover 500 to 400
600 100.0 0.1002 -62.9111 1.3054 400 !
600 2000.0 0.1002 -62.9111 1.3054 400 ! Platte 6 Perrine Regio start

is there maybe an error in my rotation?

Best regards and thanks to everyone in advance