This is a discussion on Summer Time / Shorts and Fit Tee + Glock 30sf IWB within the Defensive Carry Holsters & Carry Options forums, part of the Defensive Carry Discussions category; Crossbreed Supertuck; you'll love it! I agree, shorts and T-Shirt works real well. Two week trial if it does not work for You return it, ...
I don't consider a fitted T to be light clothing for hot weather. I like something a bit looser, with a collar. It not only looks better, but ventilates better. I live 50 miles inland on the Texas Gulf Coast, so I know a few things about heat and humidity.
I don't carry Glocks anymore, and don't carry far behind the hip IWB, so I can't advise further. I did carry a G29, identical in size to a G30, for a while, but not IWB.
Others have tossed out plenty of holster recommendations so I'll just add a few general opinions...
1) I'm not sure how you define "fitted" when it comes to t-shirts but loose clothing is your friend. This doesn't mean you have to look like you're wearing a sack...you can still look decent and carry a full/compact-sized gun. I carry a G19 under shorts and a t-shirt or hawaiian/camp/guayaberra shirt in the summer with no problems.
2) Why do you choose to carry in the manner you specified (5-6, palm-out draw)? Carrying that far behind you requires much more joint-articulation than if you were carrying farther forward...even 4-4:30 would be an improvement.
3) Give some thought to "Appendix carry." In addition to several other advantages, I personally find this to be the easiest way to conceal (provided I don't have to tuck in my shirt).
"Being a predator isn't always comfortable but the only other option is to be prey. That is not an acceptable option." ~Phil Messina
If you carry in Condition 3, you have two empty chambers. One in the weapon...the other between your ears.