Interesting. What was your boil time in cold temps? How does the stove as delivered (not inserted into the twig stove) fare in breezy conditions?
For canister stoves I use isobutane/propane in lower temps because it has much better cold weather performance. Anything with butane is terrible as you approach the freezing point.
As an aside, canister stoves work better at higher elevation, not worse. The difference between the internal canister pressure and the ambient air pressure is greater because the outside air pressure is lower. Perhaps the observation of poor performance at high elevation was due to the lower temperature, not the lower ambient air pressure of high elevation. I have used canister stoves above 11,000' elevation on many occcasions, sometimes down to freezing temperature, and they worked quite well.