Welcome to AC Jazzz, and welcome to the Open Baffle Circle!
I think that experimentation is the the key here, and that the QTS of 0.5 certainly gets you in the ballpark.
As for wings, and driver placement, it is open to interpretation. I use the driver up higher on the baffles, as per your link, and find it fine, WITH bass augmentation. Others have commented that they find the lower mounting, and associated angling of the baffle satisfactory.
As for the horizontal baffle on the rear, directly over the driver, it is simply a way to add effective baffle, without adding to the actual baffle.
Anything that keeps the front and rear wave apart qualifies as effective baffle. There are pros and cons for the use of such rear obstructions, as you start to go away from the true figure 8 dipole model, and use U or other frame types.
For wing sizing, I simply experimented. Some intelligent folks around here suggest the use of mdf as your first baffle, and use cardboard etc as the wings, so you can optimize your structure, as you play around. Then you can make an appropriate baffle out of whatever material you choose, and know how it will sound in your room, with your gear, to your ears etc.
All the best!
