Recently, I attended a lecture by natural beek Chris Harp (though he uses Langs instead of TBHs), and one of the things that he said was that he creates "visual walls" for the bees so that they know where to build their comb. I'm not explaining it well here, but you can see my notes on his lecture at:
Originally Posted by Ambassador
. Based on that info, I think it makes sense to add empty bars between the comb, but I can also understand that you may not want to give them more space than they can defend.
What if you just put most of the empty comb all together, but put an empty bar between the last two combs on the end(s)? That would give them some comb to get started, but it would also guide them to where you'd like them to start building.