Luton showing the area of poor assembly.
I have removed and re-sealed the two front cross trims. They were both in good condition with no water seepage showing.
I have come to the conclusion, At the pointer 'Water seeped in here' it is the only weak point on the Luton. Where the water seeped in and filtered down inside. It is a point where the front cross trim ends each side. A small water fall is generated at this point right into the only week point on the Luton.
I have found this to be the only weak point for water ingress in the motorhome, as the rest of the construction in the Luton have plates which overlap, and I would expect water to fall away from these areas.
It is as I have found after removing the front cross trims.
As can be seen the rippled panel rounded area, a portion of the Luton, overlaps the GRP and has no overlap for itself,
At this point I found there were no screw supports on the inside of this GRP section. So waterproofing relies entirely on the sealant and tight screws. As this is not possible, due to the GRP material, I suggest during re-assembly, the 5 points should have screw plastic plugs inserted to hold the screws tight. Fit them before trim assembly. It is no use drilling new holes to secure the trim as the problem will re-occur as the screws pull out later on. Probably due to contraction and expansion.
Take care with the selection of your plastic plugs, too hard then they will turn with the screw!
Before I started this repair there was no indication of any fault on the exterior!