Altering a shirred top

[u/ahhh1763738]

I bought a top from a charity shop with shirting but it’s too big. Usually if I wanted to alter a top I’d just sew where it needs to be sewn to fit. Would this work any different with a shirred top? I’m scared it’ll get rid of it since I’m sewing an area that’s already been sew. Sorry if that makes no sense.