there's one with a round secion that fits into the D/O and uses a longer QR, so avoids the eyelets which are better used for the guards (do need a bit of spacing to clear the caliper tho) i forget who makes it offhand – tubus?
old man mountain also worth looking at, and blackburn have an axle-fit rack due soon.
we tried a chainstay-mount disc for this bike and the issue is that a road compact crank q-factor + std MTB or Cross chainstay length = heels hitting disc caliper every time. so we chose minor faff in rack sourcing / fitting over major faff in pedalling.. any further issues though and you can mail me direct, enquiries@genesisikes.co.uk