Thiel Cs 2.3 with neodium Tweeter of CS 2.4

Cut your losses and get some new speakers, preferably from a brand that is still in business.

There is a Thiel Owners thread on this forum. I would suggest searching for that thread and then posting your question there. A few members have rebuilt their crossovers and someone may have experience that will be useful.

If I were in your situation I would probably buy the pair of 2.4 tweeters and go ahead and try them. Odds are they will fit and if you won't hurt anything if they aren't optimum. The CS 2.3 speakers are hard to beat for a reasonable price. I understand why you want to salvage them.

Thanks for sharing all that good info after the fact.  I’m out.  Good luck.