Blog Post I made on using stuffsacks.

It shows first packing it in a tan stuffsack for attaching to outside of pack, but no pics on the frame.
We use two web straps with fastex buckles. The stuffsack has web loops on the side for the web straps to pass through so sack won't slide out.

The second batch shows a blue stuffsack for an internal frame pack with the bag inside.

In both cases the sleeping bags are down ones however they take up less than half the stuffsack and clothing and extra gear are included inside. In fact the foam pad, sleeping bag and clothing fit in the external frame stuffsack. So a synthetic bag should fit excluding some of the other stuff.

For outward bound courses, the students could fit a 20d synth bag, long underwear and socks, climbing harness and helmet in their stuffsacks and then put at the bottom of the internal frame packs.

http://blog.owareusa.com/2013/01/10/stuffsack-use/