Preventing cabover rot in the first place?

I had a leak around the cabover vent, too. I stopped it by just putting more Dicor self levelling caulking on it. I didn't remove the old stuff. When I do that, I will put Eternabond on. Also, the seam along the front. I noticed that the water pooled in an area beside the vent. It seems the crossmember holding the roof and vent up is bent or broken, likely because I didn't know how flimsy the roofs are and worked up there without running planks side to side. To deal with that depression temporarily, I opened a joint in the ceiling below so I could get my arm in. I pushed in a piece of wood long enough to run over top of the cross pieces from one to another. It sits there without fastenings and eliminates the depression. Something worked - no leaks for a year now. I intend to one day open that ceiling and fix it properly, probably with a metal cross member screwed onto the damaged one.

Thanks for the reminder - I must Dicor the clearance lights again.