Put me in the camp with those always wearing an undershirt no matter the weather. I'm a good-sized fellow and live in Georgia and if it is not just as hot as Texas it is close enough to make you not care. I carry appendix in a KSG Armory rig and most often a 5" VP 9 with SRO. I like the Columbia-style fishing shirts but my go-to is this type from Callaway Golf. https://www.callawayapparel.com/coll...s+Big+and+Tall
Golf polos are just as ubiquitous as Columbia Shirts and do not need ironing if you don't leave them in the dryer. I wear them untucked and they are easy to clear when presenting your handgun from an AIWB carry position.