I carry a G19 in a tuckable Galco holster, summer or winter. You don't say how tall you are yourself, but I'm 6'3"/210. All my long sleeve shirts are tall sized, won't touch one that is not. For short sleeve shirts, while it takes some searching around, I find those that are longer as well in the hem. I go both tucked and untucked, sometimes stepping up to an XL shirt but typically size L depending on the cut.
Bottom line is it sounds like you're buying the wrong clothes and not dressing to the CC needs. Bass Pro/Cabelas and Sierra Trading Post are great sources for tall sized shirts. Most "Big and Tall" shops don't even stock size L shirts from my experience, so I don't bother much with them.