I don't think I could do the feather joint, as room for finishing would be tight. In fact, hoping I can get away with sanding all the panels, mask the joining edges, apply the clear, remove masking, and glue in. The interior walls of the cabinet are going to be painted and finished differently.
Next time, I will think a joint like this more thoroughly before starting building. I agree, would prefer to make the structure self load bearing.. was just too excited to get started on this one! So, I already made the panels, I used walnut and don't have enough scrap to make a new center panel. Walnut is hard for me to get and it is $$$$ so I am going to at least try gluing the joints with clamps/jigs. If it fails, I guess I'll make a new panel. I think I'll be OK though.