Thats ingenious. That helps a lot, because like you, I do not have a scupper. Does it stay mounted pretty firmly?
Yes it does. Plumber's GOOP is much stronger than silicone. Leave about 3/8-1/2 " of plastic on the cup to GOOP down. It's watertight, so there's nothing but water between the trans. and the hull. I have a portable Lowrance fishfinder that came with a suction cup mount for the trans. I removed the suction cup, attached the bracket to the plastic top of the Chinese food container. Fill it with water, snap it down, then remove it to take your FF home. The cup stays on the yak. I have another kayak I use, so I stuck another cup on that one. Have fun.