I expect delivery of new hot tub. I have in place a 6 inch thick concrete reinforced pad which served as foundation base of a previous 500 gallon wooden hot tub.. Ontop of that 6 inchpier blocks upon which rest 4 x4's crossed by another layer of 5 4 x4 's with spaces between. They were added to raise level of new hot tub. Question-- Do I need to put on top of 4 x 4 's a layer of decking planks for a 79 x 79 hot tub? Can the new hot tub rest on spaced 4 x4 's?