Mrmb, yes, I do have some success to report. I mounted the acoustical foam on the back of the frame about 10" behind the panel which keeps it mostly out of sight. Based on my way of thinking, because of the concave design of the rear face of the tranducer, placing the damper closer to the source may be more effective for this design.
Anyway, listening to solo guitar seems noticeably improved. The most notable of these improvements seems to be an enhanced center stage effect. The overall presentation seems less complicated and cleaner. I really don't know how to describe what I'm talking about but, although the differences are subtle, I can definitly say that I like it better.
The biggest enhancement to my listening enjoyment, though, is my having been fitted with a good pair of hearing aids. I recommend this approach, btw, to anyone having difficulty finding problems with their equipment. It might be your ears. I know this because I spent over a year replacing components, interconnects and speakers to correct what I perceived as deficiencies in my system.