Guess this might be a question for Mike.
You guys may recall me mentioning making something like this for LOML.
I've just worked out the weight of a lead roof (using Code 3) for the size of building she'd like (approx 8m x 3.7m) and it's about 500kg. Looking at the construction it seems to be very open inside without any beams stopping the walls from splaying out. It looks smaller than ours and so I'm wondering if the extra length of our long walls will need some internal ties between the opposite walls ?
Or maybe make the roof plates (if that's the right word) out of a long torsion box ?