MarkBC - I guess so...I am not very familiar with solar set ups. My truck has the one 85W panel up top. I have an extra solar plug in the back for a portable panel. I am looking to add more solar to the system for the times when I am camping in one spot for a few days at at time. I currently have a 30 amp controller. It is an Enerwatt EWC-30 model (PWM, not MPPT) module.
I called a shop to install an additional 100W panel on the roof, but they are recommending a minimum of 10 gauge wire from the roof and connecting the two panels in parallel. I am not sure how much voltage drop I may end up with if I decide to leave the 12 gauge wire and avoid the cost/effort of rewiring to the 10 gauge through roof and camper.
Don't mind doing it if needed, but hate the idea of rewiring if not needed. Lookylou - sounds like you haven't noticed any big issues, so maybe I will just start with that and go from there...