Just put a set of "prototype" Thomastik jazz rounds on my fretless F, and while i love these on a fretted bass, I am underwhelmed. I wonder if anyone has found a "piano string design" string that sounds good (I don't really care for the La Bella's that come on them).
I used the rotosound version of these several years ago and besides the pain of having to put the ball end on manually I thought they were pretty cool and sounded good. Not sure about for fretless though. I actually just put F-Bass brand strings on one of my basses today. They feel really good but I haven't gotten a chance to play them amplified yet. I think they are mfg by LaBella, like you said, but the gauge is different from the super steps.
Did you get the Super Steps? I personally like these strings on my BN5. Did you order directly from George or have you found a retailer that is stocking the F Bass strings?