Just received my first order from ModernTailor, the $20 trial shirt.
Used measurements from my best fitting shirt.
Didn't realize I clicked "normal" fit instead of "slim" until looking at the order now.
So far I think it's not too bad for the first try. The sleeves could be quite a bit narrower throughout, but the body fits pretty well despite my mistake of choosing normal fit instead of slim.
I think I'm going to go with the small collar next time in addition to modifying...