I was asked the question about how I bonded in the side vent louvers.
I started by folding up some aluminum angles. They attach to the louvers via nutserts and stainless button head cap screws. On the flange where they attach to the body I drilled a bunch of holes to let the fiberglass and resin flow through the bracket.
To bond them in place I mixed a paste from vinyl ester resin and glass microspheres. I try to use vinyl ester for repairs where possible as it's the same resin that the body was originally laid up with. The microshperes are a powder like talc but very light weight. Mixed in with the resin it makes a strong lightweight filler.
To hold the louver in place while the resin cured I just used a paint stick and a couple of cable ties. It seemed to work well.
Once the resin had cured I removed the louver and then laid chop strand mat over the bracket with more vinyl ester and thoroughly bonded it to the body.
After it's all done make sure you carefully clean out the threads of the nutserts before putting a bolt in. Run a small drill and a tap through them. If you try to force a bolt into a clogged thread it can spin the whole nutsert.
Cheers