The 6" RMH last year never really warmed the mass of the bench since the 100 feet  1/2 inch copper coil extracted most of the heat from the barrel through a water exchange system heating radiant floors and domestic hot water.

This year, a preliminary test indicated extending the bench would be necessary, since the added heat from the 8" system, even with an extra 60' of copper added to the coil, made the exhaust  too hot, so i added approx 7 feet  of ducting, extending the bench about 3&1/2 feet.

the plan is to add another 60' copper coil at some point which should bring exhaust temps down closer to 100 degrees, currently the exhaust is running about 130 -140 F

This iteration of the RMH heats water much faster, and with a continuous blaze there are times when the very small water circulating pump from last years system will run almost continuously when heating the radiant floor. This has shortened the time the stove has to run and increased the speed with which it heats water for showers etc. I am very close to having instant hot water, although not in the quantities necessary for a regular shower

This will likely become a permanent fixture, although there may need to be some changes to the firebox, and i will probably remove the barrel during the off season to add  extra insulation to the heat riser, which currently has about 2" of a formed perlite /fireclay mixture.

The main firebox/ j tube construction was local clay/perlite mix, and the firebox and first part of the tunnel shows extreme wear, although critical areas have been reinforced with fire brick,

I anticipate replacing the whole firebox with the split fire bricks, stood on end to give better wear, and reuse the perlite clay mix, by mixing with fresh clay and refractory cement. These items were not available when i rebuilt this in the fall, and now that i have located an inexpensive source will be using them more frequently in future builds.

also, i have been in touch with a "maker" who belongs to a club in Charlottesville who was very enthusiastic, and hope to be doing classes in RMH building very soon.

That's all for now