MSR Reactor

Weekend of 9 MAR on the Spearhead Traverse, we saw a skier using a one inch strip of copper foil around a canister (not sure how thick it was), he also attached a strip of foil from that strip up to the burner. The canister sat in an insulated cozy of sorts (bottom open). He said he had been doing this on many ski trips. I wanted to stick my thermometer in at the canister, but was too consumed with futzing with my own stuff.

I'm glad you got your real world test.
I tried copper wire over the flame and arround the canister on my Bluet years ago. No success. I also tried the warm water. A bit of success but not worth the hassle. The best result was had when I dug a channel below the stove and lit a candle underneath. Never got anything warm enough to explode.

In twenty years, I've used a canister stove once in the snow. I'm still more impressed w/ my wisperlight, a two liter pot, and the MSR heat exchanger. Fill it and walk away.

Weekend of 9 MAR on the Spearhead Traverse, we saw a skier using a one inch strip of copper foil around a canister (not sure how thick it was), he also attached a strip of foil from that strip up to the burner.  The canister sat in an insulated cozy of sorts (bottom open).  He said he had been doing this on many ski trips.  I wanted to stick my thermometer in at the canister, but was too consumed with futzing with my own stuff.

this is the way to go!

flatten a 1/4 inch piece of copper tubing and wrap it around the shape of a fuel cannister, with one end extending to around the heating element.

i think i first heard about this on colin haley's blog, it works good.

Another option is to get the msr windpro II and use it in inverted canister mode. I haven't used mine extensively in the cold yet, but I did some testing on a ~10F windy day and with mostly used canisters from a 0F freezer at found the setup can achieve whisperlite like performance without messing around trying to keep the canister warm.

It works because the propane found in good cold weather fuel blends (msr, snowpeak) will stay as a gas in the top of the canister and foce the liquid butane out through the valve on the bottom of the inverted canister. It requires a stove with a preheat tube (like the windpro) to vaporize the liquid so it can be burned as normall. By comparison, even with the regulator in a sol or reactor you are still just burning the fuel you can boil off which becomes harder once you burn off all the propane in the blend.

any thoughts/opinions of the improved efficiency of the hanging stove?

I use a jetboil and hang it inside my tent. I have never been able to burn through a complete canister so I cannot attest to the actual efficiency and performance; BUT on a two night stint at Muir, I used about half of an 8oz canister for two people.

I normally use the Flash pot (middle size). For super lightweight alpine climbs / ski mountaineering trips I'll use the Sol (smallest pot). For more than two nights out, or more than two people, I will use the Sumo (biggest pot) to maximize the amount of water melting at a time.

I also NEVER put ONLY snow in the pot. Think about all the time and fuel you waste while just developing the heat transfer medium for later ... ALWAYS put at least an inch or so of water into the pot to start so that you have the initial driving force for the heat transfer from the pot to the snow.