Having made two kilts out of 10 oz. duck, I feel your pain.
You want to include the reveal (1.5") + the pleat depth (3.75") + the backside of the previous pleat (3.75"); so, yes - 2 x 3.75 + 1.5

If I'm reading your post right, you currently have a pleat reveal of 1.5" and a pleat depth of 1.875" (your 3.75" is halved between the depth of your current pleat and the back of the previous pleat).

Did that help?

Easier version: what Steve said.