Do you guys think a drive spacer will help my slip# i have high slip# 20-21% just looking to get this number down

it may. you may also have other issues, hook rocker, bad prop , etc,,, .

I installed a 1" spacer on mine and it really helped. I had 24% slip and it went to 14%. You need to check and see where your prop shaft is to the bottom of the boat.

How do i check this x-dimension and what should it be?

measure from the bottom of the boat to the center of the gimbal.