XL guy t-shirt to t-back girl tank

Ok, tomorrow is Warped Tour and I needed a cool shirt. Found this gem at Buffalo Exchange for $8.
Guys extra large t-shirt, and I want to make it into a tank top for girls.

The secret is to cut the same length of material under the arm pits, the shoulders and off the collar. NO SEWING!! Just scissors and use a piece of cut fabric to tie the back into a t-top. SCORE!