Hi Neal. Like i said nothing has change in the house, the article you mentioned is about a conversion. If fact much less weight now. I removed huge amount of material from the flat ceiling including drywall and stringers, ceiling tiles. It has been used like this for years. Inside the space of the knee wall was also a massive amount of loose insulation.
All the weight was on the beams before - now it is more supported by 2x6" and the new structure. It will 26x5= 125 sq on each slope. 1/2" drywall weight about 1lb so total about 300 lbs not 3000.
The drywall weight will be held by the 2x6's still that means there is half the amount of drywall that was there for the last 20 years. All the drywall just hanging right from the main beams, now it will be on the slope, much better support. No weight on the beams. Remember the sagging is caused by long pass water damage.
In summary there is much less weight on main beams and attic structure now. The structure has been significantly beefed up due to the 2x6 added support.
btw, what you know about declaring this place a heritage building? I have a feeling it could be due to the cord wood.