flush fitting windows

Gents Just installed the plywood floor in my campervan conversion and hopefully dry fitting the RIB seat this weekend for Christmas transportation and i noticed this staining around the one wheelarch edge of the ply, its only on the drivers side and on touch does not feel wet? Is it just...

After reading various threads I understand that the OEM flush windows have had problems with leaking. I also understand that there now aftermarket ones available and have found a few via searches. My question is what are the best ones?