I had the FWC roof rack and the Zamp on z bars screwed into the roof. A lot of work to take off, but I laid down 3 100 W HQST flexible panels with velcro. The velcro is on the sides and front, leaving an air gap and flow path. I've got a simple USB temperature logger that I will slide under a panel to track temperatures to see if my system provides adequate cooling. If we were regulars in Baja, I would have somehow raised the panels up a good half inch or more, but we tend to head North - for three years running, we encountered snow storms in August (note my avatar). Going from about 45 lb to about 18 lb, my wife can now raise the roof.
A single large panel will weigh significantly less than two panels. At 300 W or so, you can consider home solar panels. When I was researching panels, I came across a 320 W for $150 on Craigslist - they had ordered one panel too many. That panel would have fit, but 45 lb was more weight than I wanted and it would have meant more holes in the roof. Vic Harder has such a panel on his rig. If you know someone who is installing a home system, they might be able to order an extra panel for you. In bulk, panels are cheaper.
The wiring should be straightforward. The Zamp controller will have two pairs of terminals, "Solar" and "Battery". Just transfer the wires to the Victron "PV" and "Battery", respectively. Make sure "+" goes to "+" and "-" goes to "-". If the wires are not already labeled (FWC began doing that a few years ago), its wise to label the wires before moving them.
Be sure to buy the Victron from one of their dealers - all warranty is handled through dealers. I got mine from PKYS (https://shop.pkys.com). They were fast, the price was good and they rate well.
I mounted my Victron MPPT behind the kitchen cabinet, out of sight, but with Bluetooth, I can see all parameters. You can even turn off charging with bluetooth when you are working on interior wiring.
A battery monitor is also a good idea. There are a lot of very good but expensive ones out there (I have one) but consider a low cost option that Will Prowse (youtube) has found. It's probably not as accurate as the $200 Victron battery monitor, but at $42 it answers the same question. When I had AGM batteries I would just glance at the meter to know if I was on the path to draw them down below about 50%. And over the 5 years I had the AGM battereis, I could see them being drawn down a bit more each year. They still have some life in them, but my LiFePO4 will most likely outlast me, so I switched. The Victron MPPT can handle all types of batteries, including ones I had never heard of.
https://www.amazon.c...,aps,441&sr=8-5
...maybe... 
