I have covered the gaps with duct tape but it is wearing out and I want to make a more permenant fix. I used one tube of caulk and it did not go too far. It may take another 15-20 tubes to finish.
I do have access to the floor underneath so I can put duct tape or 1/4" ply to close the gap. I am just looking for something that could be used to fill the gaps.
Right now, I can't find any large tubes of caulk, just the 10.1 oz tubes and cheapest is about $2/ea.