So, chaos reigned along the entire battlefront. The French were able to make an ordered withdrawal with their remaining forces and the Russian were able to seize Altdorf and rendezvous with the supply train.
All in all another great game. John said he'd doubted whether the Russians could break through the French. Sadly for me he was wrong, but it was a tough edge of the seat game for all that. I'm still not 100% sure about Black Powder for this project. However, I've mucked about with the rules and unit statistics a fair bit and they do seem to work and give a good, if not better, game.