I was going to respond to your comment that "even the railroads would help that freight over the hill with an extra engine rather than have all of the needed capacity connected constantly" by saying they'd only put in a helper district if there really was no other way. You've beaten me to the punch, however, with your observations about heat loss. To that I'd add that from my experience with a Mag stoker, I wouldn't be too concerned about running it harder, especially if the burn is being monitored and the stoker doesn't need to run hard often. Also, I know precious little about hot water systems, but it wasn't obvious why the tempering would be needed if the unit was only run on demand. Squeezing out a few more degrees of temperature differential seems like it could help.