Man F# and G are super low .
I'd be going actives that low really . thats why most bass players use em
Actives come in most 8 strings, and many 7s. I used them for a while and swapped them out. Active guitar pickups like the Blackouts try to give you a grainer, high-output signal but that's not really what you need. EMGs just don't sound very aggressive or accurate or alive and don't really have tons of precision in the lows. In fact there are a lot of extended range BKP users because passives can be so much more accurate, tight, detailed and balanced than some mass-produced boardroom-engineered active.
While I wouldn't be one to discourage extended range tunings, 26.5" is rather short scale for F# - you end up needing a very big string on those scale lengths just to keep a decent amount of tension, and then it's so big it sounds dark and not very balanced with the other strings. This is the sort of thing baritones are made for, longer scale length = thinner string for the same tension, and a snappier sound to help with the lows. (For the record, a 64 for F# or G is definitely NOT what I would call a "heavy bottom," even at baritone lengths. I'd recommend more like an 80, but then, you'd also have to pick where you're tuning. You can't expect the same string to hold the same amount of tension when you're tuning it at A and then F#.)
So maybe a bright and tight ceramic like a Cold Sweat would help keep that low end under control, but your pickup can't fix your string. If the string is too loose and dark sounding then you have no choice but to go to a longer scale length.
