Why would you want to squat using a Smith?
The only reason for using a smith machine when squatting is if you're doing front squats.
If you're able to do normal free weight squats, DO THEM!!!!!!!!!
You'll grow better, be stronger, pull smarter women, save the planet etc.
Nothing contributes so much to tranquilizing the mind as a steady purpose - a point on which the soul may fix its intellectual eye.