I just checked with Renogy about adding a 50 watt panel like the one in my suitcase kit. They said the kit is designed for those panels and controller and they don't recommend going over 80% of controller amps. So the 10 amp controller should not exceed 8 amps. With 3 50 watt panels at 2.7 amps you get 8.1 amps max.
So if I want to add a 50 watt panel like those in my suitcase kit, do I buy just the panel and wire it up to the existing controller, buy a 20 amp controller like the one I have and wire them together or buy a panel with a controller ands not wire them together?