Apply masking tape to the metal amp wall around the four sides of the terminal opening. I applied tape about about 2-3 mm. away from each side of the opening, so the caulking would stick up to 2-3mm away from the opening.

Now, apply a bead of silicone caulking around the edges of the hole. The caulking only needs to be about 1.5mm high to work well. That should be just enough to keep the new terminals close to the amp wall when you fasten them down. Allow 24 hours or more for silicon to dry properly.