We used RTV Silicone for small holes. If needed, we put masking tape under the pan to catch drips until the Silicone dried.

Because we repositioned the engine pan, we had a few larger holes. Based on Mark's suggestion, we covered these with pieces of rubber. We used RTV Silicone and rivets to attach the rubber.

We cut rubber pieces from an old Azusa inner tube from our Flightstar.

After prototyping with brown paper, we positioned the rubber over the hole and cut slits when needed so the rubber would lay flat.

Then we 'glued' the rubber down with RTV Silicone and riveted it in a few places.

Yellow arrow: This is the opening for the oil sump vent tube. We have a golf tee in the hole to protect it from the silicone.