When I read the reviews of the hot rails pickup, they were full of comments like: "hot, hot, hot...dark and muddy, not bright...better for dirty than clean tones...strong mids and lows...heavy mids...never a truly clean sound, always crunchy,great for distortion". that sounded to me like a pickup that might work OK for bass. As a bonus, because of the rail design there are no pole pieces to worry about aligning with strings.
And then a gent offered to send me one he wasn't using, as he'd played it in a Bronco but later sold the bass and put the stock pickup back in.
I don't have a practice for a week or so, but I'll know more after that.