How about taking a feeler gauge, measuring the gap from the top one the transom side between the boat bracket and your platform bracket, then getting that thickness of ss metal or aluminum then cutting it to proper width and length , putting a bend on the top end then inserting it on the water side between your platform bracket and boat bracket. when you want to remove just tap up on the bend of the piece of metal..........I think some one already has this........just use a feeler gauge to determine the thickness and length you need