These appear to be acoustic suspension. You may want to do more with the back pressure. i.e. a tuned port. Am I missing something? You may want to look at Nohr speakers for additional design features. Are these internally braced or damped in some way, or are you fairly certain about any resonance issues.
In the end there is only one real parameter that matters if all else -connectivity, durability and safety, are assured and that is....
How do they sound?
Esp. in comparison with competing products.