124 Spider,

I would not use a single speed chain. Under load your boom tube will bow (slightly). Now your timing chain has to flex as it is engaging the rings. Multi-speed chains are made to run like this, single speed are not. There have been reports of single speed chains coming off the timing rings because of this bow/flex of the boom tube that puts the timing rings out of alignment.

Tailwinds,
Charlie
S&S Santana Beyond

When we used a chain, I went to an 8-speed chain because it was cheaper (at the time) than the 9-speed the bike came with. I carried an 8-sp & 9-sp quick link then.