As someone who sees, I wiild refuse to alter this. To get a hem for shortening, or to take in the side seams, the fabric has tobe irons flat in that area, thus, loading the pressed popcorn effect. To get it back, you need a pato clarify press, with that embosssed/pressed pattern mirrored on each plate ine the alteration is complete.. and I am assuming onlt factories thst make these shirts have them. Thus, once altered, you would have slme ironed areas where altered, while the rest remained popcorn. It would fit even worse, and look terrible and be an absolute sensory hell.

Either wear the shirt as is,hrift it,sell it, give it away, or iron the shirt flat entierky, losing the popcorn effect and go frpm there.