If you can find a sufficiently long 16mm tube of the right thickness in the US for decent price, I will. I found a CF tube but the price is obscene. The Rookie/Roo spar isn't long enough. BTW, in my experience, the Rookie/Roo spar isn't strong enough either. I've bent three, including two with the dowel inside. The Formost tubes are way thinner than the Roo/Rookie tubes.

Right now I'm thinking of doubling the tube with a full length 1/2" wood dowel or aluminun tube but it would have to be glued into the stub tubes because of the loose fit.