Hi Craig B
I seem to be in exactly the same position: looking to fit an awning rail to a T6 LWB high roof. Not so many of us high-roofers!
I've been wondering whether to go with the Vamoose, which I'm guessing fits to the narrow strip of accessible metalwork between the sliding door and the bottom of the GRP roof (although it must be pretty slim to achieve this), or to fix a generic P-section rail to the GRP roof (by P-section I mean C-section plus fixing flange, if you see what I mean).
Must admit I was leaning towards the latter, for simplicity and cost reasons, and was just deciding between 3 fixing options when I read your post, which made me back-track a little.
Have you installed the Vamoose rail? If so, I'd be really interested to hear your assessment of how well it works and what it was like to fit!
In case anyone's interested in giving an opinion on GRP fixing methods, should I go for the generic option: I'll fix with Sikaflex 522 in combination with one of these mechanical options:
1. Self tapping screws. In this case I'd slightly countersink to avoid the screws lifting and 'spidering' the gelcoat, use a drill a fraction larger than the screw core size to avoid pressure on the plastic, and lube the thread with Sikaflex for clean thread cutting and sealing.
2. M5 machine screws and the smallest rubber Rawlnuts (8mm diameter, as I recall), which would have the benefit of providing an anchor from the rear of the GRP skin with no need to access from the inside of the roof (I made the mistake of installing roof insulation prematurely).
3. M5 bolts through the GRP and also through spreader plates/ large washers, which would be bedded onto the inside of the GRP with Sikaflex. I'd us Nylock nuts and locking washers on the inside, as access to tighten any loose nuts would be tricky once I've installed the interior cladding.
So, any thoughts on the Vamoose on a high roof Transporter and/ or my GRP fixing options much appreciated!
PS: Re suppliers, you mention Magnum. Think I've ordered three bundles of kit from them since I started my DIY camper conversion and have found them very good. Good products delivered very promptly with only one minor mistake, quickly rectified. Grasshopper Leisure have been very similar.