In addition to the all new larger midrange version, there is a new 4.5" midrange driver available for Apollo, Ulysses, etc. since early 2021. I have had it (along with the newest tweeters and the Stability Bases) on my Ulysses since it was first introduced and it sounds great in them. More recently Lou had his engineer figure out new Xover pieces to upgrade the Apollo 11 as well, but he is so swamped with work that he doesn't really have time to promote this upgrade. However, he was willing to let me try an in-the-field upgrade to mine.
First, let me say that if you have experience as an electronics technician and are handy with tools this is something you could manage, although replacing the drivers is easier with another person to help. Lou's availability to troubleshoot is invaluable, BUT... there are a lot of potential pitfalls to this process and it would be easy to get into it and find yourself in over your head. That said, I was able to complete this in about 7-8 hours total. How much the sound improves will have to wait for a few days for the new parts to break in, but "out of the box" it is at least as good as before.
For me, this was far far better than the option of sending the speakers back to Lou, not even allowing for the fact that he doesn't really have the time to do this himself. He really wants me to emphasize that this is not a project to undertake unless you are quite confident in your skills and experience.