Soft dome tweeter replacement for Thiel 3.6s

I am a long time Thiel owner and still in love with my Thiel 3.6s. They are driven by Mark Levinson 23.5 amp and Cary Audio SLP 03 tube preamp with NOS tubes.

I have a question about replacing Thiel 3.6 Vifa tweeters with soft dome tweeters. Rob Gillum at Coherent Source Service sent me a pair of soft dome tweeters. After replacement, my immediate observation was that slight harshness in the upper octave has disappeared compared to the original Vifa tweeter. Imaging is still excellent, but I feel that they were ever so slightly better focused with the Vifa tweeters. I am talking about nuances here, not differences as clear as day & night.

I know the late Jim Thiel (May He Rest in Peace!) was very particular about his crossovers being optimized to each driver. So I am just thinking even though soft dome tweeter works, the Vifa tweeter may still be a better fit. Appreciate your experience/feedback if you have replaced tweeters in 3.6s.

p.s. I am going to ask Rob to replace the ferro-fluids of the original Vifa tweeters and hope that will reduce the harshness/brightness. After all these are more than 20+ years old