took XL, looks almost the same size as my IH V-neck size M!

waiting it to dry after the first wash and off we go 

Hello I have a question about sizing.

I just ordered my first IH item, a IHPT-04 7.5oz Plain V-Neck Loopwheeled Pocket T-Shirt which fits perfectly in size M.

However, the opening on my existing shirt is 53,1cm for size M, where the opening for IHT-1600 is about the same in size XL! Other measures are also comparable from 7.5 oz M to 11oz XL!?

Should i get XL for IHT-1600, especially when it is said 11oz gonna shrink a bit?