Here is something you can do for the pin holes:
1. If they are very small, put some tape under the floor where the holes are. That will keep the POR15 from dripping through the holes. Then paint from the top. The paint will harden, and the pin holes will be gone.
2. If the holes are a bit larger, use a bit of fiberglass matt. First, tape on the bottom like in step 1. For each hole, cut a SMALL amount of fiberglass into very small pieces. Paint over the holes and place a small amount of fiberglass in each hole. Press the fiberglass down until it is smooth. DO NOT GET POR 15 ON HANDS OR CLOTHES. It will eventually wear off skin, but it won't come out of clothes. Then paint a second coat. This way the repair will not be noticeable. For worse areas, I agree with the others who say use larger pieces of fiberglass. You might be able to see the fiberglass fibers, but who cares, since it is covered by carpet.