I've been reviewing the specs in more detail, since those plans are the actual design/construction plans showing every numbered piece of wood.
I've colour-coded to show how some logs are single pieces, and others are two pieces:
So wall C, the bottom 3 planks are split where they rest on the pillar, interleaving with wall 3.
On the other hand, as you can see in wall 3 the lengths
are a single span running from walls B-D, pieces 008 and 016 both being over 5m long:
This makes me wonder if the upright is really needed in the first place - there are 7 logs of this length all stacked which is a massive timber if treated as one piece. Again, I will be asking an engineer but I'm wondering if those pieces can be bound together to form a super-member rather than being stacked.
In the meantime we're still chasing the manufacturer but they have been slow to respond, and have now informed us it has been built and shipped to the UK. The timing makes me cynical that they've deliberately not answered our questions so they can ship the thing and say "well, it's done now".
This seems to suggest getting them to address the design is now difficult without a significant delay which we cannot afford, so how would people proceed in that situation? They will not ship it to us until payment is completed so would you lot demand a price reduction to allow for making changes? Or what?