Hi 'Nando,
Like Gene I like your presentation a lot. It comes very near the original function and is much better than using modern iron parts. Everybody will grasp the idea that the wood sybolizes the missing iron.
I would only suggest adding one little thing for completeness: a wooden wegde or shim to open or close the rear emptiness - just as would have been the case when the chamber was placed in the original recess of the breech of the barrel for firing.
Best,
Michl