Agree that not everyone needs a full 4-pannier setup, and that a bikepacking setup may have advantages on an off-roading setup, but as I said I'm not sure the racks are all that well engineered - even on the rim brake version there's not a huge amount of triangulation. I'd be happier with a Tubus Tara-style loop over the rear wheel, or Blackburn-lowrider-style mounts either side of the seatstay. Of course you'll most likely be ok - otherwise I guess they'd have already had reports of breakages - but if you're already going full custom for the frame and bags, why not sweat all the details?
Both of which are triangulated Blackburn-style of both sides of the fork blade? The Fern racks are attached on one side of the seatstay by a long-ish bolt, which is going to see a bending load if anything bumps the luggage from the side.
Agree that not everyone needs a full 4-pannier setup, and that a bikepacking setup may have advantages on an off-roading setup, but as I said I'm not sure the racks are all that well engineered - even on the rim brake version there's not a huge amount of triangulation. I'd be happier with a Tubus Tara-style loop over the rear wheel, or Blackburn-lowrider-style mounts either side of the seatstay. Of course you'll most likely be ok - otherwise I guess they'd have already had reports of breakages - but if you're already going full custom for the frame and bags, why not sweat all the details?