Plastic gutters on T4 Trooper Water Ingress.

Bought my T4 Trooper about 6 months ago, and so I could fit a Vango Airbeam drive away awning, I riveted C channel to the body, to fit this I removed the plastic gutter trim, then replaced it fitting new plastic screws.
All seemed to go well......however...On site, awning attached to C rail by Kador strip,(proper job) I found water ingress from the guttering   . When I had refitted the plastic gutter trim I did not apply any sealant as there didn't seem to be any in place when I removed the trim.
My question is, do I need to remove the trim and seal the bottom edge? also what sealant should I use?
Its clear that water can access the trim where should it come out ? Hopefully not where it comes out now, right above the sliding door  

The water exits these gutters above the windscreen and at the back next to the tailgate. You can remove the gutters and reseal them but there will be work needed both on the van and the gutters before you can refit them.
I removed them as part of a windscreen pillar repair and the topic is in this forum with pictures, I will try an find you the heading.

T4 Trooper Gutters, with pictures

Cheers DaveSedge,
I have done some work on them now and refitted them using some sealant. Whilst on hols in France, during some heavy rain found a small leak but otherwise was quite successful.