Both areas will be 3/16" to 1/4" thick, well below the 3/8" minimum. In my shop the forward mounts would get reinforcing with 3/16" flat aluminum, 4" x 10" simply bedded in bondo (polyester body filler) to the underside. I pre-drill the plate place it up under the deck and use a simple bolt & nut to draw them together while the filler cures. The aft mounts needs the same treatment however shaping the aluminum into the radius is usually done with a ball peen hammer and beat into shape until it fits well then bed with bondo like the front. The tricky part is getting the aft tower base mount to fit the outside curve of the deck, this is very important, I have made custom spacers from starboard (marine plastic) to fit the deck. Remember the aft legs are pressing down, so the if I have a 2" diameter base, I will make a 3-4" diameter plastic interface to spread the load. The forward mounts are trying to pull upwards & out.
