Hi everyone! Thank you for your suggestions. Been a little while so figured I'd pop an update here.
- Fork is the CoLab Cross from Cyclemonkey. Rated for tandem use / 400lbs, 15x100 TA.
- Wheelset is coming from Wheelbuilder.com, 36h DT Swiss hx491 rims rolling on their 350 Hybrid hubs. Also up for consideration were the Velocity Cliffhanger rims but they're in short supply at the moment and we can't afford the wait.
- Drivetrain is 2x11. I've got a set of old truvativ husslefelt triples, and the BCD suits Shimano mtb rings (with some filing of the tabs). These will get cut down, drilled and tapped to suit my boy. 2x rings are 26x38 with a 44t timing ring; paired with 11-46 rear cassette. This exceeds the stated capacity of the SRAM GX rear derailleur so will use a Wolftooth adapter to keep everything happy, but I hate cross-chaining so probably not necessary. Shifting duties performed by a GX groupset.
- Hope V4 brakes with 203mm floating rotors.
- Front crankset will be my UT6800 paired with a narrow-wide 44t.
Chain line - I'm hoping I can find a short enough isis spline for the rear crankset to try and get a decent chain line. I'm planning to install the front crankset and then experiment from there, I feel like I need the frame to experiment with what fits as I'm not sure about the clearance at the chainstays with different spindle lengths. Put the bottom bracket in and then go from there. Unless anyone has a better suggestion?
Cheers,
Owen