I suppose when you say you are boiling out the air bubbles your are really using a vacuum pump to evacuate the air? (You know that not everybody works in the air conditioning field and has access to a vacuum pump!).
I hate to admit how long I have had silicon brake fluid in my 66 Alpine. Its got to be over 20 years and still holding. I remember it was a good name brand of silicon fluid. I think it was a GE product? In any case fellow motorists, I am going thru the car now and will be rebuilding and changing the fluid. However it is still working. Duel cylinders does seem like a good idea.
I think and someone correct me if I am wrong that the boosted original cylinder was .75 (3/4") bore and the non boosted series I and II used a cylinder with a .625 (5/8") bore. I have driven my Alpine thousands of miles using the 5/8" bore cylinder and no booster and stainless covered flex hoses and have been really happy with the braking.