I already carry appendix. And driving and sitting have never bothered me. Sometimes I do need to adjust my holster after sitting but after that it's good. It may also be that I am on the skinnier side of things too. So my belly never gets in the way!
I haven't used one personally but a special forces co worker of mine says he loves it. The 'claw' keeps the rig and more importantly the weapon pulled tight to the body for concealment. Rigs with these types of attachments are truly meant for AIWB but can be worn elsewhere if you like. What I have found is that most holsters that claim to be AIWB are not built to be appendix carry, but are more IWB. Don't get me wrong, many people make it work without a claw but with one your weapon will be far more concealed. As far as sitting comfort, that all depends on your ride height along with the length of your gun. A great explanation of this is in the page... Everything You Need to Know About Appendix Carry
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