We are in the process of installing a DXV Freestanding bathtub. The instructions say to apply a 3/8" bead of Liquid Nails to the bottom of the tub to adhere it to the floor. The tub is not yet glued down. It feels a little rocky. The floor is flat but if I push down on one side, the other side goes up, maybe a quarter inch. I don't really like the idea of relying on the liquid nails to fill the small amount of space, even if it only works out to be an 1/8" on each side. Tubs I've done in the past have always been in a mortar bed, but they were not freestanding. I feel like the small amount of space that needs to be filled is too small for mortar. Looking for opinions on whether thinset would work better, if I can just go with the liquid nails and be fine, or if there is another better option. Thanks.