I have 3 190W panels on my 2019 FRF3, was able to locate the support beams to make sure they were used when possible to drill into, made sure to use the hardware to munt, plenty of the right dichor , ran the wires down the plumbing vent an routed into my storage bay for the charge controller.
I would not rely on just VHB tape as some on the internet.
Word of advice, if you are leery of drilling into the roof, you can take your panels to a reputable installer, I had one of my panels mounted for ~$120 in Northern CA. I still ran my own cables.. Best of luck
2019 FR3 33DS Motorhome
Travels California Coast & Beyond