Not very often that I’m impressed by any homebrew engineering that I see on this forum, but genuinely massively impressed by this!
First thoughts were “The BB’s will be a bit bloody high”, but then of course realised that on a Tandem that’s more of a positive than a negative. And of course, the ridiculous chainstay length of the 29er Giant Anthem Swingarm is neither here nor there on a tandem either.
The fact you’re achieving 6″ travel out of it also is cos Anthem’s normally have a 165mm eye to eye shock with 38mm stroke to achieve 4″. So you’ve got 50% more stroke, therefore 50% more travel.
Top job anyway! I badly want a go on that… 😀