After OSW, we visited the Fresno layout and I saw a WP caboose there that I thought I may have seen on this forum. Beautiful job Chris.
Regarding the urathane for casting cabooses ---About ten years ago I cast up several kits of O scale SP wood cabooses using the stuff that Micro-Mark sells. Worked quite well and the there hasn't been any warpage or deterioration so far. Micro-Mark sell it in small quantities, which I prefered because of the short shelf life this stuff has. The photo is of the castings for one car.
Charlie