Bathtub framing question – GreenBuildingAdvisor

So have a framing question. I have a 57in wide wall and need to fit a 60” tub. Back wall of tub without water lines is the back wall of closet. Walls are 2×4 as stated in plans. Measurements are off because original wall opposite of closet was not only crooked but also built with 2×4 on the flat so between plumbing the wall and building a 2×4 in front to plumb it, I lost 3 inches. So am I allowed to:

remove bottom somehow to squeeze tub in, almost as it if I framed a door.

Removing the 2×4 on each side of tube and building a 2×2 wall on each side instead