Tub deck question

REXAMUS

Just looking for input to see if anyone catches an error in my math.

Putting a tub in a three wall alcove and tiling the front instead of having an apron.

Tub is 20 inches from the feet to the top. The drop-in rim is 1 1/2" less than that and the integral flange is 1 1/4"

The front portion should be 20" - 1.5"(rim) - 3/8"(tile and thinset) - 5/8"(cbu and thinset) - 3/4"(plywood) = 16 3/4" for the front wall.

Then the two side walls and back wall should all have a ledger board at 20" with no tiling or anything needed.

The tub is also going to be set in a bed of mortar but it won't affect the height since there will be no mortar under the feet.

Anybody see anything wrong with my math?

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