Roof structure info for installing roof rack: R-Vision Trail Lite 235s B+

[BGood]

I previously posted about this (http://www.rvforum.net/SMF_forum/index.php/topic,115228.msg1041629.html#msg1041629) but received no responses.  Since then, I have obtained crossbars for the proposed roof rack and researched more about non-structural roof components, but am reluctant to begin drilling holes in the roof without advice from someone who has successfully completed a similar project.

After consideration of several alternative storage options (ladder, trailer, etc), the best option for my situation appears to be the use of horizontal crossbar extensions which require the kayak to be stood vertically against one extension bar, then lifting the kayak's opposite end onto the opposite crossbar extension with a stepladder.  But to do this, I need to securely mount the two crossbars to the RV roof.

By removing light fixtures in the cabin interior, I have a good idea about the non-structural roof construction (see attached), and concluded that it would be ill-advised to simply bolt my crossbar mounts into this thin plywood and styrofoam.  Likewise, I am reluctant to: 1) bolt clear through to a rigid backing anchor on the cabin headliner, or 2) screw into the apparent cross-framing members of the roof which appear to be on 4-foot centers.

Can anyone provide any further guidance on this project?

Thanks

 

[Zowie]

Hi I was cruising info on crossmember on my old Traillite Crossover TLX170 and came across your post, so I registered to the site to write you my reply I hope your project went well. I tried just feeling aluminum crossmember, using stud finder with no luck... I could see one when I removed fridge vent but it’s just that one. Close to the edge of where wall and roof meet(maybe 2”?) have solid aluminum corner under rubber roof. I’m trying to locate cross members to mount strut channels, and then solar panels on them. I hope your project was successful.
my next move is to wait for a hot sunny day, max out AC of TLX170c and see if I can detect temp difference as aluminum should conduct heat/cold better than insulated non-structure supporting area.