we based our pack on jay ham's SUL Pack but altered it slightly.
First we used a 0.75oz spinnaker Which was on sale at about £5 a meter, great for this sort of project and our first myog.
We added a hip belt, A Velcro roll top closure to keep out water, added 2 side pockets and 2 Lycra stretch panels on the back to take a sleep pad as back pad, also didnt bother with a front pocket.
A kinda cross jay ham, mariposa type pack!
Heres some pics.