Installing replacement roof vents without "clamps" or screws?

[pauloh]

I could use a little advice. I’m in the middle of replacing my TM’s two non-powered roof vents following a hailstorm a while back (photos of taking them out are attached). The original TM/Ventline vents I’ve removed were a “clamp-in” style, clamped to the ceiling with 4 screws inside the TM. The Ventline vents I purchased while traveling in another state are not clamp-in, they instead are designed to be screwed to the roof (part #V2092SP-28). They test-fit perfectly though, so I’m planning to go ahead with using them. (The FantasticFan vent which is still intact on my TM is apparently installed with this type of screw-in perimeter.)

I’ve cleaned all the old caulk off the roof, and off the synthetic wood vent “risers”...I’m ready to install the new vents....

I’d rather not drill new holes into my roof to hold down the risers or vents, and am thinking of just using a good adhesive caulk (possibly 3M 4200 I have on hand) to attach the risers to the roof. Then use short screws to attach the vent to the risers. Considering use of 4-inch Eternabond RoofSeal around each vent/riser up over the screw heads to add some additional “security”. Or at least caulk all edges with silicone and at each screw hole to seal those up.

I’ll be putting MaxxAir vent covers over the whole thing...these are attached to the vent itself so there will be some drag in high winds/going down the road. Will it all hold with those risers attached only with an adhesive such as 3M 4200? A possible alternative for more security would be to use long screws only at the corners of the vents, penetrating into the roof skin. Any suggestions welcome, thanks.