Have you decided what too do about your speak Tony? I really dont know what else you can do, but I do know the Tamiya units do have what you called ( a sweet spot). Like I said before you should find it around 80% volume as per Tamiya. But like I said before my Panther sounds really good at all volumes. The box is quite large even compared too the Tiger speaker box.  Once you get the hull layout done maybe you can shew horn in a larger custom made box. If you go this route just remember too use some padding inside the box and vent it well. Speakers need too breath inside there enclosures.