Ed:
A 12 pounder Napoleon light field gun was normally not used as horse artillery. It was too heavy for use as horse artillery. The weight of the bronze tube was 1,225 pounds and the weight of the gun carriage was 1,128 pounds. The combined weight of 2,353 pounds was too much for the horses. It would have killed them if used for rapid movements such as horse artillery service. The 10 pounder Parrot Rifle was much better for this type of service since the weight of the iron tube was about 900 pounds and the gun carriage was 900 pounds, for a total of 1,800 pounds. As it was, life for a horse pulling field guns averaged only about 7 months.
I still vote for the 2.9" Parrot in answer to your question.
Ron