Best thing to do to fix this is to make sure the drain holes are all unblocked. Have no idea how to do it or what you would need to push down the drains to unblock them!
My old 2600 VDP had an annoying leak everytime it rained, the drivers side front corner of the headlining would start getting really wet & drip from the corner onto my leg, if it rained heavy it became a raging torrent onto my leg & the floor! I thought it was the screen leaking, so I sealed the egdes of the screen with bath sealer, but it kept doing it, so I can only assume it was one of the sunroof drains that weas blocked....
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Auto Vitesse, gonna be a beast!