I have a pretty new (less than 1 month) recumbent that I've been having some shifting issues with that I think may be directly related to the chain length. FYI, with my 'bent (SWB USS) the boom is adjustable for the rider's leg length.

My question is after finding Sheldon Brown's method for chain sizing.... it would seem to me that the chain length would be too short for the rear derailer/tensioner if I only have 1 full link after running the chain around the largest rear cog and big ring.

Is this just a 'visual' misconception? I don't want to break the chain down more than necessary, but I do want to fix my problems.

I don't have very much recumbent experience but I can tell you that on a conventional bike the "one inch" of chain rule works fine. When the bike is in the big/big combinaion the derailleur arm s pulled virtually parallel to the chainline and "one full link" is just the right amount.

The big-big sizing method, is large chainring and large rear cog, without threading it through the derailleur + 1 link.

This is how park tool describes it as well. With complex recumbent chain runs, you may have to resort to eyeballing it with the chain through the derailleur in small/small and big/big.