Just finished this for my daughter. Not a super-weight weenie build, but I was pleased how it came out. Building it with my daughter was a lot of fun and I don't think she's ever liked a bike so much. The setup is fairly "modern" with a 1x drivetrain, wide range 9-36t cassette on a custom hub, 120mm XX fork with RCT3 damper, slack (for XC) 69 deg headangle (via offset shock bushing and modified rear shock), low BB, relatively long top tube (for the rider) combined with a short stem. The 600mm wide flat bars and 26" wheels are certainly "old school". It still needs a top chain guide (cf supplies on the way for a custom unit) and the fork steerer cut when final fit is confirmed. A clutch type zee rear derailleur is also on the way, so +70g there. Final weight will probably be around 9.45kg with chain guide and zee RD, but its perfectly rideable now.