"(PeteCresswell)" wrote
I've got a cylindrical cavity about 1.25" in diameter and 1.5"
deep that I plan to plug with a cylinder of styrofoam that's
slightly smaller in diameter.

I missed how small this repair is the 1st time around.

I'd make the repair directly using fairing putty and get on with it.

You can eyeball a 1 oz serving of mixed epoxy.

I use 1 oz serving cups sold in restaurant supply shops for this task.

Mix up 1 oz of epoxy, then transfer to a larger container (Paper
coffee cups work for me) and thicken with micro-balloons.

If this is a thru hole, cover the bottom with duct tape, then apply
about 1/2"-3/4" of fairing putty in the bottom of the hole and trash
the rest of the fairing putty.

Wait 24 hours, then repeat.

Continue until putty is proud on both sides.

Allow 36 hiurs to cure, then sand flush.

At the outside, you will use 3 oz of mixed resin and a 1/2 cup of
microballoons.

The trick is to remember that a 1/2"-3/4" coat of fairing putty is maz
or it will go exothermic.

Lew