Yeah, I thought about the hat thing, but truth is, I seldom wear one. Plus it would put the ITR too high for my liking.
I like your idea about feeding it through the fabric of the shirt, but fear that this will cause the ITR to snag, and resetting after I get a break would be a royal pain in the ass.
After pondering this as I type, You may well be onto something there! Hidden in the design of the shirt could be a small eyelet, like those you thread your laces through on your shoes. Made of the right material, or coated with something, this eyelet could allow the thread to move through the shirt with little to no snagging. Reset after a break would be a lot easier too (Although admittedly would mean a trip to the bathroom to remove the T-shirt!)
Hmmm, Maybe we should manufacter this!

Make a fortune! But then this is a public forum!
So, on behalf of us both. ***Manufacturing Rights Reserved!***
What do you think? Ideas on a design that would hide the eyelet?
Phil