Great info - thanks!! So let's see...since I have been failing in my quest to find truly great, slim-fitting undershirts/plain white T's, perhaps I should just order up the Sea Island knit and get one made to specs! How many hours does it take a good tailor to make a t-shirt? 2? Except now that I think about it, there was something about the collar of a tee-shirt (the slightly elastic part) being a royal pain if you wanted anything other than the cheap ones that exist on most everyday t-shirts...I'm sure others on here know way more about that than I do.2x is usually the starting point (not including sales/clearance), with scarce / in demand goods going up to 3x.
Time to google!