jonandfamily - we look forward to your report. Here's some additional back-story about that soft dome.
We developed that UltraTweeter for the CS5 in 1988. It had all of Jim's advanced techniques, and exceeded our expectations. The CS5 had woven lower Kevlar drivers, and if an appropriate soft upper midrange driver had been found, we would not have gone to aluminum. However, the MB Quart 2" aluminum dome did the job better than anything else, and we didn't have time to develop our own driver for that use. Market pressure. The aluminum tweeter had more predictable response particulars and the metal domes dissipated heat better. That's where we went.
When trickling that tweeter down to the CS2.2 we reconsidered the fiber dome to mate with the pulp midrange. Jim went with the CS5 tweeter and gradually migrated to all aluminum diaphragms rather than all Kevlar / fiber / etc.
So, I consider that soft dome tweeter as native - it was co-developed with the hard dome and should be very good, with possibly some advantages. The only one I've ever heard was in comparative evaluation during 2.2 development around 1989. I'll be getting a pair for comparative measurements and listening tests.
As a general caution, heat dissipation is a big deal. The soft dome don't be a heat dissipator like the aluminum dome is. Don't over-drive it.
Keep us posted.