Thersa, I assume you are talking about the Dicor. Dicor is not really intended to fill holes, it is designed as a sealant for around items IN penetrations, such as roof vents, ac units, etc. It is also used as a pliable adhesive to hold things in place, such as wires on roofs from solar
panels, antennas. (Not really designed for that, but it is a side effect that is commonly used) It is a Lap Sealent..it makes a nice barrier wher the seams of the skin on stickies come together, and it is also good with ridgeline seams on motorhmes where the sidewalls meet the roof, as well as around the seams from wall to roof on stickies with gutter rail. If you have an awning
, you will no doubt find a bead if it all along the top of the rail the holds the canvas in.
There are two kinds of Dicor like this. Self leveling, which is thinner than the non leveling stuff I used. It actually seeks the lowest points (Like water) and oozes down into open spaces. This is the good stuff for roof sealing points, and anything on a horizontal surface. If you squeeze a 2" diameter lumpy blob an inch high on a horizontal surface and walk away.. when you come back in 5 mins, the blob will have nicely leveled itself into a 3 inch diameter smooth surfaced thingy with a skin on it. Thats why it works so well "Up Top". This is the stuff I need to finish the job properly at the top of the drip cap. It will seek and find any gaps not filled by the butyl and will seal the butyl as well.
The non leveling stuff is used on vertical surfaces. It does not seek lower ground and is pretty much gravity defiant. It stays where you put it. It also makes great "thread lock" that is removable. Thats why I dipped the screws in it, and it forms a nice little gasket under the head when some of it gets pushed out of the threads when tightened down.
The problem wilth filling holes on a cosmetic surface is that it is not very pretty. It doesn't sand easily, if at all. I used it because it was something I had on hand, and it was going to be covered up by a chunk of metal. No harm, no foul. Eventually, it will need to be resealed. How long, I can't say.
When exposed to air and the weather, Dicor will become hard and crack in about 3-5 years. It needs to be redone..this is the dreaded roof sealing stickie owners get to do as due diligence. The GOOD news is that you can simply dicor over the old stuff as long as it is clean and free of loose bits. This can be done several times, but eventually, the whole wad will need to come up and you start from scratch. Unlike silly cone, it is not all that hard to remove and it comes off cleanly.
After all that..my answer to your question is, no, I wouldn't use it for YOUR repair. The surface you are fixing needs to be smooth. I would see what I could use as a dowel in there, cut as flush as you can and use fiberglass resin over it and sand flush.