I think the biggest surprise on clearances was in the tunnel where we had to quickly create more space. The use of balsa made this easy and reminded me at least what a great material that is. Cutting holes in the model if we had used styrene would have been more problematic and lead to collateral damage .
The other major clearance issue was in relation to the third/fourth rail, and the stock pick-up shoes. Difficult to get this right with the stock in Essex, and the track laying in Elgin!