Thanks for the response, Tom. Your description is very close to what I have, except that the self-supporting feet don't run the entire length of the tub. That concerns me since it leaves the center vulnerable to flexing.

my new drop in tub has green foam on the base, and this is supposed to make it level. So do I still need add an additional base?

Depending on the persons size in my opinion. I weigh 230 & it had way too much flex between the pad/feet without mortar for me. Put in a small scrap wood dam for the mortar sandwiched both sides by construction plastic so mortar won’t attach to your tub & sub-floor. Deep soak Jacuzzi tub going in today after framing & surround.

Was that a Jacuzzi Tub?

Was that a Jacuzzi Whirlpool Tub 42 x 73" by any chance?

Jeannie, this is a 20 year old thread, the people that commented are probably long gone. Start a new thread if you truly want help.