It it's business casual and tucked shirts in an office environment you may have to consider a smaller weapon. I can't carry at work but as a Pastor in Missouri, I've had to figure out how to carry without a cover garment. I can wear a suit coat on Sundays but in the summer it's VERY hot with that on and looks odd to leave it on all the time. You can go deep with the various deep concealment T shirt style items but I can't imagine how anyone can truly carry a large weapon without it printing or getting uncomfortable under their arm all day. Perhaps they wear a larger, almost baggy shirt?
IMHO, the more casual the dress the easier it is to conceal unless you add a suite coat or sport jacket. As for the tuckable holsters I can not believe that anyone can call that concealment when you have two clips on your belt with nothing else? I believe people in my office would be very curious about that. The better shape you're in, the harder it is too because that bump doesn't blend in with any love handles.
I too have used Smart Carry and it works very well with small guns like a J frame or keltec p3at so long as your pants fit somewhat loosely in the crotch area. Being as tall/large as you are, that should also help your comfort factor when you sit down. With a Kahr P9 It' make it too tight in the crotch area on me (5'7") with dockers.
I think the options for hot weather business casual dress are limited unless you can leave the shirt untucked. I would think pocket carry with a smaller weapon would be an option for you. I've pocket carried a Airweight J frame but it's still a pretty good chunk to ride in the pocket.
Not much help but it's hard. There's a reason secret service guys are always wearing jackets in 100 degree's. I even tried ankle carry but that was the most obvious method of carry I've tried.
Hope you find what works. I carry a Kahr P9 whenever I can dress w/come kind of cover garment. Other than that, it's a keltec p3at in a pocket holster w/an extra mag in my weak side pocket. Good luck!
Gideon