Yes, same chassis. Saw the same article. Beautiful job, wasn't it?
Regarding your question about balsa. Most modelers shy away from it, because it's generally difficult to cut without tearing, even though it sands easily. If you smear the outersurfaces with thin (the one with a viscosity like water) CA, it can be cut to a very close tolerance with a razor saw, and shaped with sanding sticks. I used it to scratchbuild the carriage for a Gribeauval 12-pdr gun, and was pleased with the result: lighter than basswood, I didn't need a coping saw to cut/shape the parts, and I got a great "real wood" effect after it was painted. I'm going to use the same technique to improve the carriages of the Lifelike Civil War gun, and the Naval 32-pdr, as well. Hope this helps, Rob