Just thought I'd update the thread.
The GHS Precision Flats are still on the '08 American Standard. They seem to be breaking in really nice. They are mellowing and evening out from string to string little by little. The D and G are still a little bright, but as we all know, they will mellow out over time.
This is the second set I've had on this bass, same gauge (45-105). The first set I commented on how the Low E sounded liek crap. Thud, not thump, dead, dull, lower in volume and just so far off compared to all the other strings. I had strung the strings through the body. I took the strings off and tried them on another bass strung through the bridge and also put them back on the original bass and they still sounded like garbage. Put on another set and strung them through the bridge and the balance was much better even when brand new, consistent in tone and the E string was so much better/night and day difference. Maybe I just had a bad set, maybe I screwed them up going through the body. Who knows.
The strings have a great round, thumpy characteristic to them. I tried some LaBella Deep Talkin' Flats on another P (Classic 50's) and they seem to be a little more polite and even sounding from string to string out of the pack, and have a totally different character than the GHS. Not better or worse, just different. The GHS just seem to have a sort of dirty, growly tone to them. They sound great played with fingers and muted with foam, or palm muted and played with a pick.
Another thing I've discovered too, is not every P bass likes flats. I so badly want to have flats on my Classic 50's P, but with any kind of flats it just sounds uninspiring. With rounds the bass is ridiculously resonant, thumpy and alive.
Also, it also seems like no matter what set of flats Ive tried, be it the new Dunlop set, GHS< LaBella, Chromes, etc., the low E always seems to sound a little "different" in it's tone compared to the other three. Maybe this has something to do with the gauge, as in once you get above a certain string gauge things start to change. I've also read this elsewhere where a well-known player/reviewer had commented in an article that this is just an inherent characteristic of flats.
Either way, I really have no clue what I'm talking about and it's all an ongoing learning process for me, and a test of patience, letting the strings settle in and enjoying how they change in their sound over time.