I fixed a 2' X 2' area upper rear corner on the side of my current '97 5er. I drilled several holes at the top of the delam spot so the adhesive could run down.
I had the trailer in my trailer barn and used the barn side wall and a 2 x 4 wedged against the wall and the delam spot. That was 18 years ago and looks great.
IMO this was a mfg process defect as there was or is no leak.
The trailer didn't come with a drip or awning rail. After fixing the delam spot I bought 65' of EZE Gutter for both sides of the trailer. The EZE just about covered the drilled holes. However you have to look close to see them under the EZE gutter lip.
"good judgment comes from experience, and a lot of that comes from bad judgment" ............ Will Rogers
'03 2500 QC Dodge/Cummins HO 3.73 6 speed manual Jacobs Westach
'97 Park Avanue 28' 5er 11200 two slides