On topic, some guidelines I can offer:
Your top end will drop if someone's standing in front of you, but the shirt itself will *generally* not impede your results. Also, your bass response should be a little more accentuated, but again not due to the shirt.
Biggest issue is clothing noise. What you trade in freedom of your head, you pay in ability to move your body. Work on practicing this at home and changing options (e.g. windscreens for no screen and different types of clothing) before you do it in the field to see what you get for noise.
I gave up stealth taping because of shirt worn mics (among other reasons). The hassle just wasn't worth it to me unless I needed some serious camo against security and *really* wanted a copy of the show.