Just an update on this for those that are interested.
Gave the BBMB its maiden run today. Ran some cleaning feints with some old herbs thrown in through it just to see how it performed and check that there was no scorching. It's a winner!
Scythe, you were right. Not too much evaporation from the outer boiler at all and the outer boiler didn't hit a rolling boil until the end of the run and the product was well into tails and coming off too slow to bother continuing.
I am going to need to figure out a way to anchor the inner boiler as it becomes slightly buoyant once the level drops low enough.
Very happy with how this turned out and am looking forward to the first absinthe run.
Cheers,
Prof. Green.