Yes, I have an FNF 2-channel ebonite feed in my 743 FA, which improves ink supply considerably. I ordered the feed the same day I ordered the pen.

I haven’t bothered getting one for my 912 FA; when I ordered the 743 the 912 ebonite wasn’t then available… apparently it was unusually tricky to perfect. While it’s now available, I don’t use my 912 FA enough to warrant the upgrade.

It’s an interesting area. Some thoughts, for the incredibly few who might possibly care: