store sells the tape for elephant hide seams, some folks have questioned it's sticking quality as it is less expensive than other sources of same general product. Hopefully they will weigh in with link to those other sources to give you a choice if you desire.
Some use 3M spray on glue (77 if I recall) as a supplement to the scamp
tape built in adhesive, available at big box home improvement & most hardware stores.
I have the scamp
tape but am just now getting ready to test a couple of small seams to see how it sticks. Already removed the old yellow crud covered stuff that was there.
On the belly band it's not actually a "seal" it's just cosmetic (or supposed to be) when the top and bottom half of a scamp are put together they fiberglass the inside wall at the seam so it "should" be totally water tight. The aluminum belly band just hides the lip that is on the top and bottom when they come out of the mold.
People do caulk the top of the belly band to keep dirt from collecting there, acrylic latex caulk works well. Just need a tiny bead to fill in the gap between edge of aluminum and wall of trailer. And don't do if it's really hot and sunny, the hot aluminum can cause a near instant cure of the caulk. (found out the hard way)
That said mine had a huge snake of silicon caulk that took two days to remove and it turned out was keeping water from a chip right at the seam that did leak. Chip was hidden by belly band, but looking at band after locating leak I could see it had scraped something right at that spot.