Equivalent to/improvement on 19mm MDF

[VantheMan]

Regarding my Mk 2 boxes. I´d like to make them a bit less behemoth-like (after Totem arros, anything is too big) and I have spoken to the designer and he has given me some new INTERNAL dimensions to work on so long as I respect the previous baffle step/port dimensions. With a view to reducing them a bit more, say, in the width could I use some other material for the sides (Marine Ply springs to mind or anything else for that matter) which, for a given thickness might be roughly equivalent in whatever parameters are considered important (rigidity etc.) to the 19mm MDF I used originally. Also would a sandwich of 2 thicknesses of MDF or whatever be equally as suitable/stiff as just one solid piece for a given thickness. I am thinking of sandwiching the front baffle and cutting different diameter concentric holes with a tank cutter thingy to avoid having to use a router (which I haven´t got).

Grateful for any help,
Chris