I had an extra front end from an '04 Honda 600RR, the last year for conventional forks, and a spare set from a Hayabusa. It was far easier to modify the parts and fit the Honda unit, rather than the USD forks...no need to re-invent every wheel. Now the Double has a fairly modern front end with adjustments for pre-load and damping.
The bike was never designed for wide modern tires and in order to comply with the current "race" rubber rule, we are left with very few options and they are all 17" and fat. I managed to squeeze in a 190 series rear tire into the swingarm but that left us with very little adjustment, and the left side wall did eventually rub during tire growth. I sorted through a couple of bike wreckers trying to find a used swingarm that we could modify but didn't have any luck. We looked at several different aftermarket manufacturers and we still would have needed them to make a "one off" swingarm for our application, so we are just going to make the "one off" ourselves. Because the rear frame is so narrow and in order to keep the sprockets aligned, we need to use a jackshaft. If the coupler wasn't in the way, it would be a simple matter of using an outboard bearing set up off the countershaft. The design is pretty much finalized, we will make most of what we require on the CNC and Richard will tig weld it together.
I saw the bike last week and the body was sitting loose on the bike. The front engine's header will be a challenge and may require a "blister" on the right side of the body. We did decide to try and run the exhausts out the back of the bike, rather than out the side, to try and keep it clean. We hope to move the 2 side oil coolers (cylinder heads) in closer and gain the necessary clearance for the body. The front engines' troublesome main oil cooler will likely find a new home in the nose of the faring and will be fed air by ducts. The rear engine's main oil cooler seems ok where it is and out of harm's way.