Just picked up a new Wells Cargo MW6 4x6 enclosed trailer.

I have an 86 pound kayak and the aluminum roof rack Wells cargo offers only is rated for 50 pounds so the first thing I plan on adding is a Yakima roof rack (1a raingutter, high rise spacers, wide body).
Where should I mount the wide body bracket (A or B)? The roof is polymer with an aluminum frame. I can get one screw from the wide body attachment into the aluminum frame but the other will just be bolted to the polymer roof. Is this strong enough? I've seen this discussed elsewhere and the dealership guy was telling me I could bolt it into the metal strip (labelled A).
Here is a similar trailer and it looks like he mounted to the roof/frame (B on my trailer).

Rewire 4 pin to 7 pin terminal connector (allow use of prewired Auxillary terminal)
National Luna Portable Power Pack ($560)
National Luna Weekender 52L Fridge/Freezer SS ($1650)
Hardware
Roller Drawer and Fridge/Power pack mount
Rod/paddle holders
Accessories
Eezi-Awn Series 1000 2.5m Awning ($545)
I have a marmot ground tent that I really like but may end up going with a RTT [Eezi-Awn Series 3 Family ($3380) --or-- Gran Sabana ($1650)].

I have an 86 pound kayak and the aluminum roof rack Wells cargo offers only is rated for 50 pounds so the first thing I plan on adding is a Yakima roof rack (1a raingutter, high rise spacers, wide body).
Where should I mount the wide body bracket (A or B)? The roof is polymer with an aluminum frame. I can get one screw from the wide body attachment into the aluminum frame but the other will just be bolted to the polymer roof. Is this strong enough? I've seen this discussed elsewhere and the dealership guy was telling me I could bolt it into the metal strip (labelled A).
Here is a similar trailer and it looks like he mounted to the roof/frame (B on my trailer).

Initial plans:
ElectricalRewire 4 pin to 7 pin terminal connector (allow use of prewired Auxillary terminal)
National Luna Portable Power Pack ($560)
National Luna Weekender 52L Fridge/Freezer SS ($1650)
Hardware
Roller Drawer and Fridge/Power pack mount
Rod/paddle holders
Accessories
Eezi-Awn Series 1000 2.5m Awning ($545)
I have a marmot ground tent that I really like but may end up going with a RTT [Eezi-Awn Series 3 Family ($3380) --or-- Gran Sabana ($1650)].