Personally I've just never found IWB appendix carry comfortable, especially when seated. If you're main concern is carrying while driving the semi have you considered a shoulder holster system? They're not for everyone or every situation but when seated for long periods of time they can be just the ticket.
I carry a 5" Mil-Spec in Gary's MaxCon V and it's without a doubt the most comfortable holster I've ever owned. I've even fallen asleep on the couch while wearing it and his double magpouch (several times) ... and I prefer to think of my extra poundage as a "pork chop storage system." You never know when you might have to skip a meal so I choose to be prepared for that eventuality - that's my story and I'm sticking to it!
Jack