Scuttle moulding screws

I have been sorting out the rain ingress to our Symphony.
Quite a successful exercise. I have fitted the drain hose from the collector so that it stays in place without leaking and have improved the fit of the collector to the cross rail. Better seals to the windscreen wipers has stopped ingress onto the battery tray. Just have to repair the existing damage now!

My question is: does anyone know why the fasteners holding the scuttle cover are so strange? I would call them cryptic. They are hex cap heads ad take a 5mm A/F hex key, this together with their proportions would indicate a 6mm bolt or screw. However, they have a short length at 6mm, then are M3 threaded. A trap for the unfortunate as they are unable to stand much torque. I suppose the 6mm part limits the engagement and so pressure on the moulding. Is there any other reason?

The poor cover of the holes in the moulding allow water in. I have fitted soft washers to improve the seal. Two of the screws are corroded and one tapping is stripped;I will tap this out to M5

Has anyone any experience of these parrts?
Bill

Has anyone any experience of these parrts?
Bill

Only in as much as removing them to seal the scuttle hose!
Just took it very easy, but they all came out.
Wire brushed and 'copper slipped' the threads on refit.

PB

Thought they were torx! some of mine were stripped out or sheared off. Replaced with stainless number plate self tappers.

Frank