Personally I would skip the USAT rail joiners and go immediately to rail clamps. Either Split-Jaw or Massoth/Trainli type clamps. The Massoth/Trainli type clamps are very unobtrusive when installed with the screws between the rails. I prefer Split-Jaw clamps for getting power to and from the rails. I bought my last couple of batches from modell-land.de,
100 Stück Schienenverbinder Messing 19 mm mit Edelstahlschrauben ML-Train 8188165, at a very reasonable price even when shipping is considered. I included a few other goodies in the order to help amortize the shipping!
. I think you will regret relying on the USAT joiners alone (or at all!) for electrical conductivity. I've been running track power mfx/DCC in a climate identical to Ttaannggss for more that six years now. Ann Arbor is about 75 miles WSW of Sarnia, ON. My track is mostly LGB brass. I don't have any of the conductivity issues that scare many into battery/RC. It's all in the track joinery and power feeds.