Check out the Linkwitz web site - he pretty much covers the waterfront.

For sizing a baffle, you could use "The Edge"

http://www.tolvan.com/edge/

An essential part of the concept is that you're not attenuating the backwave (dipole operation),so while putting a horn driver in a baffle helps support the lower end, it's not really what they talk about when they talk "open baffle".

Yes, you're seperating the rear from the front waves, but you still want to take advantage of the rear wave which you can't do with an infinite baffle (wall).

I don't think it's a lack of bass (at least I don't think so right now). Drum solos on Wilson Audio's "S'wonderful Jazz" sound pretty "right".