I tried Chromes on my p-bass for a few gigs.
Never could get the attack and thud that I wanted so I'm sorry, but I'm out.
Back to rounds for me........for a while.
Flats certainly aren't the cure all for everyone. And how you perceive your tone with flats has a lot to do with the rest of the gear you use and how you have it set up.
I like to think of my sound as something fluid and ever changing in that when I discover one piece of the puzzle that just clicks with me, then I find another that isn't quite right.
I played with rounds forever. My rig at the time of switching to flats was a Superfly into two 115 cabs that were more lo-mid focused. I put on some Chromes and wasn't thrilled initially playing alone, nor with my band at first. But after a couple of gigs and some tweaking of my rig I had that "light bulb" moment. I got it!
As my bass was then sounding and feeling full, yet with clarity, I knew I still wanted more...but really needed less. I didn't swap out the strings, because they were now integral to my sound. I got a Carvin BX1200. The tonal options allowed me to tweak more. And being a designer of my own cabs, I took it the next step further by building two 210/6 cabs (very similar to an Acme). So instead of trying to get more character into my cabs, I built more hi-fi sounding ones. Addition to my sound by subtracting. Just like flats did for me.
So what I'm getting at is that while my switch to flats (specifically Chromes) was an epiphany about my sound, it led to even more changes with the rest of my rig. The sound now with Chromes is nothing like it was when I first started playing Chromes. But the Chromes are now just a given and won't get swapped out for something else. It wasn't the strings that weren't right...it was other things in my set up.
It's possible you didn't give the Chromes enough time to settle in, and allow you to feel them out a bit more tonally. Not that you'd need to wait longer than you care to, but I find that most roundwound players do not give flats a long enough period of time to appreciate what they are really all about. Having done it quite a few times myself, I know all too well how that first try with flats feels and sounds. I must have tried to seriously make the switch to flats about half a dozen times or more. Something about them was appealing but it wasn't until I was ready to give up MY tonal goals for the overall tone of the BAND, did I realize just what flats do that I wasn't understanding previously. And since the switch to flats, even how I play is affected. I'm enjoying playing bass more now than I ever did.
It's more like a Zen thing now. Not only has switching to flats changed my sound, it changed my approach and philosophy towards bass. Simplified, loving the space more, letting the music breathe, getting into the groove and locking in with my drummer where at times it is difficult to distinguish between what the drummer is playing and what I'm playing (and I'm speaking tonally as well). Rhythmic Synchronicity. All because of a change to flats? Well, no...but there was a convergence of things in my life and the switch to flats and my approach to bass certainly was all part of this. I'm feeling the sound of bass in our band with my soul now, instead of trying to play my parts perfectly or even as creatively as possible. I don't think about what I'm playing any longer. It just flows.
As I mentioned (I think in my first post) Playing a bass strung with flats and loving it is really more a mindset than an equipment change. It's a conceptual change that has more to do with where you are as a bass player. It's about letting go. With rounds, trying to find "my" sound was like a dog chasing it's own tail. The less I care about my sound the more I enjoy my sound. It's a yin/yang thing.

Flats just kind of woke me up to it.