I have found that appendix IWB to be the most comfortable carry for me when I am sitting for long periods, either driving or on the computer at work. I can carry an XDM 3.8 compact all day with no problems. With a smaller gun like a j-frame, I have forgotten it is there.
I am not a fan of off-body carry. If it is mounted under your chair, how quickly and easily can you access it? If you do go that route, then just about any paddle holster with retention would work. Screw the paddle onto the frame of your chair and adjust the retention so it does not fall out.
This is the holster I use: http://highnoonholsters.com/Product_Line/_Mr_Softy/_mr_softy.html
I am not a fan of off-body carry. If it is mounted under your chair, how quickly and easily can you access it? If you do go that route, then just about any paddle holster with retention would work. Screw the paddle onto the frame of your chair and adjust the retention so it does not fall out.
This is the holster I use: http://highnoonholsters.com/Product_Line/_Mr_Softy/_mr_softy.html