Attachning GRP rear tube

[voucht]

Hi, me again

Another question about fitting the bodywork : the rear tube. I have a GRP rear tube, and a book chassis, which means that I have the 2 round section tube RP1 and RP2. For now, I have attached the lower edge of the rear tube under RP1.

Do I have to attach it to RP2 (the top tube) as well, or will the lower attach point on RP1 + the 3 or 4 attach points I will fit on D11 rail in the same time as the rear wheel arch will be enough to hold the rear tube?

I don't like the idea of having visible bolt heads on top of the rear tube, but if there is no other way...

How did you guys who fitted a GRP rear tube attached it?

Thanks a lot.