So what subs are you going with? Sad to see you already ditch the 21"er //content.invisioncic.com/y282845/emoticons/frown.gif.a3531fa0534503350665a1e957861287.gif
As far as the double baffle recommendations go...I think double baffles are highly overrated and overly recommended for setups that really don't need it. A properly braced single baffle(especially with 1" MDF) will be strong as hell. I can only see double/triple baffles being absolutely necessary on monster builds like Andrew's, or if you're doing a wall that has some very heavy woofers in it that might be able to strip screws through a single sheet. Of course, if you're running subs that heavy, you're probably running a lot of power and already have your box double or triple baffled.