Plumber installed an American Standard Vinyl 60x30 bathtub. He put in in a bed of concrete and used ledger boards around the three sides. On the front side of the tub (60 in side) it doesn't touch the sub floor or the existing tile. Basically free floating on that side. Obviously the floor is not level but the tub is level. He suggested that we just spray the expanding foam. We have tried to put wood under it but is is difficult due to the small gap and he already attached the drain!. Afraid that if someone sits in the edge of the tub it will break or drop down into the one inch gap between the floor and the edge of the tub. Any suggestions. My hubby tried to tell him this was wrong and he insisted it was fine. Tried to up load pics but it doesn't seem to work. PLEASE HELP.