Well, what is your definition of fixing time? Is it 2x the time to clear? Or what?
Also, there is a sweet spot as shown in Mees, and Mees and James.
If SuperFix and TF-3 or 4 have the same pH, something is wrong. SuperFix should be about 6.3-6.7 and TF3 and 4 should be around 7.5 - 8 or somethng like that.
Wet and dry is important, but the results are consisant within a test depending on how you do it and how you measure rates. You have to look at the back of the film. Also, wash rate is important and is determined by the fixer, and fix rate is often determined by the preceding bath (rinse or stop)
BTW, due to the average thickness of film, dry film requires about 15" for fixer to diffuse to the bottom.
Oh well, I've been doing this for years now.