Without knowing the whole story there are a lot of variables. Maybe am solar will be able to see or find out what batteries you are using. The price of heavy cable, heavy connectors and rack will probably buy one more panel or almost 2 panels. If you go to 500 watts on the rig and even if it is shaded somewhat at times it may be better than being on your toad. Toad wont be charging the rig when you are out driving.
Panels are still far more susceptible to walking away from your toad than they are from the roof of the rig. Really not enough info to figure it all out.