Your best bet will be to build the 'box up as big as you can, but leave it open (like an HRC airbox). Fitting the pod filters will give you the protection you need from dust and dirt. The large airbox will then be more of a "still air" shield, which is what you really want on a 2-stroke... unless you ram-air it, of course!!
As long as it's loud though!!
It's not the HP at the wheel, it's the Db at the ear - that's what I say! ;)
;)