Re-Sealing Awning Rails

Raytherailwayfireman

I need to re-seal the rear o/s awning rail on my 2004 ACE Award Tristar as a damp reading of 25 was picked up on our recent service. Dealer has quoted hundreds of pounds to do this so I would prefer to do it myself. Dealer says they use Butyl rubber strip,
plus Soudal Fixall, however I have been told Fixall should not be used - so what should I use? Have been looking at Sikaflex 512 - would this be the right stuff? Also been told this is not a DIY job, yet other forums seem to suggest it can be done - anyone
out there have any experience?