Bikepacking - a viable alternative to racks & panniers

I know alternatives exist, such as the SQR from Carradice or the Unirack from Manivelle, but given that my thighs are touching a seatpack, I'm fairly certain they'll touch these supports as well.

The SQR puts the bag a fair bit further back than something like the Zefal saddlepack. The bit that attaches to the seatpost is pretty much seatpost width.