Back Boiler Position

Hi there! This is my first post after a long time of reading on the forums. I am researching the best way to provide both radiant heat and hot water for a project I am working on. After reading many posts, articles and how-to's I have fallen in love with the Rocket Mass Heater concept (which I am certain is a general concurrence) and am beginning to obtain my components and materials to build one.

One component I have inadvertently acquired is a wood burning stove back boiler. It looks similar to the one in the following picture although it is much larger. (will upload pics in the morning)


I would like to know from others who have a great deal of experience where the best position for the back boiler would be? From my limited view, the boiler would have to:

- Be as close to the centre of the thermal mass as possible
- Not allow the water to boil


I am intending to hook this up to a thermal store hot water tank to provide heat for radiators as well as hot water. I would assume that the larger the tank the less likely the boiler is to boil. I am aware it sounds fallacious but this is a major concern of mine.