I have always been pretty much against flexible panels, not the idea, but the inherent problems they were having. But, if I was to look a installing a flexible panel I would look at something like this
https://www.amazon.com/KINGSOLAR-Mon...00R8SMVC2?th=1.
In general I am picking them for their use of the Sunpower Maxeon solar cell. You can find other vendors that are using them also. There are a few things in their cell design that enhance their reliability, reduce effects of shading and hotspots, backside attachments that give me some hope in their design holding up better.
I also believe when installing I would try to get some air gap between the top and the panel
8mm Twin Wall Clear Polycarbonate Greenhouse Panels | GEMPLER'S
such as jwintersteller did in this install
http://www.sportsmobileforum.com/for...-rig-8336.html
This would hopefully reduce heat of the panel and heat transfer through the interior.
Unfortunately, i don't have real test life data that would let me give a
recommendation. If I was to go down the route of flexible this is what I would look at, also it should be noted that other companies are building with the sunpower maxeon cell, such as OverlandSolar
https://overlandsolar.com/ looks to be building flexibe panels in the works. It is also pretty easy to get Sunpower (B-Grade) cells on Ebay, if you were inclined to build your own panel.
-greg