Mortar bed under fiberglass whirlpool tub - How thick??

[Terry]

I've got a related question about the mortar bed. I'm doing a drop-in tub and am about the build the surround for it and was wondering if I need to add any height to it for the mortar bed? In other words, will I be squishing the tub down until it the surface touches the subfloor or will I leave some mortar beneath it which would raise the rim height slightly?

I like the platform high enough that there is space between the bottom of the tub and the subfloor.
The piles of mortar squish out and away making the support you need.
Otherwise, the deck must be perfect in all ways, which isn't going to happen.

 

[Trek4ward]

Would you estimate that the bottom of the tub would be about an inch or so off the subfloor (lying in mortar).