Hi Phil, have a look at the images in my post here.
The guy at the store I bought the bike from cut, drilled, painted and attached a piece of steel that's done a good job of holding a normal rear rack in place.
Took the bike for a ride with the bag on. Found that with the weight of the rider (63kg) on the suspension, the bag (reasonably tall) can touch the back wheel. Had to tilt the top of the rack 45 degrees towards the seat to maintain clearance.
JT and I batted around an idea on how to attach the front end of a rack in this thread last December. It involved inserting a fitting through the rear shock pivot but AFAIK no-one actually tried it.