Well no one is making monocoque carbon tandems because the molds would be prohibitively expensive considering the number of units sold. We looked into it and could make a roughly 2kg frame but it'd take a decade to recoup the cost. I weighed all the Beyonds here and there's some mediums at 2780g. The larges and XLs are from 2900-3030. I'm hoping to beat that with careful tube selection and some minor changes. Also, despite appearances ditching the lateral tube doesn't really change weight unless you sacrifice stiffness. You have to use bigger thicker tubes and wider BB shells. It seems to be done more because it seems to be a modern look people like. I prefer the lateral tube look. Bikes have always been triangles and the big crooked square in the middle of a no lat tube bike looks odd to me.

Yes, the 160 rear end and wider cranks are a weight handicap that I'll struggle to overcome but coming from a DH bike background I can appreciate a dishless rear wheel. The special Spinergies I have are 940 & 690g. I may be able to skip using the 88g Ti QR skewers by having the axles threaded and using Ti bolts.