The biggest problem will be getting the corner clean. You already have some Bed-It Tape so give it a try, nothing to loose.. If the corner is clean is should adhere pretty well. Bed-It Tape is easier to remove, if it leaks again, than a sealant is. Ideally I would try to fabricate some tools to get in there and do a proper fiberglass patch. I often use aluminum bar stock to create custom sanding tools for hard to reach places, even a rag taped on the end with acetone or dewaxer etc...