Thanks for sharing your experience and this link. I downloaded it and will read it over the weekend.Personal experience aside, there are several factors that affect cyclone efficiency (% of small particles separated from large particles). I found this paper entitled "How to Select and Maintain a Cyclone for Maximum Performance" which discusses those factors, including cyclone design. Perhaps this paper can be of some help as you consider your options.
Mounting the blower on top of the cyclone is not an option for me now. The ceiling height of my shop is a little under 8' and a full 8' is required to make it work.Keep me posted on how you go, Wood. I am in same boat as you are (dual canister 3HP Grizzly). I am seriously considering the SDD XL to replace my Thein baffle. Were you thinking of placing the motor on top of the cyclone body?