What wire config for tri-wired speakers?

If you are going to do multiple runs make sure you go with something relatively low in capacitance. You are going to be effectively tripling the single run capacitance and depending upon your amp it could cause some oscillation problems.

The designer of the amp should be able to give some indication but there is a lot of uncertainty because you are dealing with multiple variables. As a general rule though excessive capacitance will increase the likelihood of amplifier oscillation and instability.

The cables based upon two layers of foil are long and effective capacitors. Don't use them in either long runs of speaker cable or in multiple runs where the capacitance will add up. I don't use them period but they are probably safe in short single runs for most amplifiers.

My personal opinion is that either bi wiring or tri-wiring isn't a real cost effective tweak. Especially when you are dealing with expensive designer cables. If you want to see the effects of bi & tri-wiring buy some inexpensive yet well designed speaker cable and give it a try yourself. That way you can make a decision based on first hand experience before spending big dollars on three runs of high dollar cables.