I agree with you 100% on F5 ciem which I've had for the past month and have around 100 hours on. My fit out of the box was just perfect but I did hear some sharp highs. That settled down really nicely about 40-50 hours in and has improved a bit since then.F5 is one of the most coherent tribrids I've heard. But you need many hours to let the planar treble settle down.
This is one IEM where almost every review I read is different. I'm also one of the only people who seem to have reviewed a custom set, which is strange given it's a Custom Art IEM!
I think the uni will sound very different to the CIEM tuning depending on tip choice, which is probably where the variance comes in. For me, the custom is definitely not basshead - not even close, and has less bass quantity and quality than Z1R (which to me isn't basshead either, so I guess YMMV).
I find the mids perfectly tuned with outstanding timbre - this is CA's strength. Treble is the divisive part; initially it was too sharp and spiky for me. With many hours of burn-in and a custom refit for seal, treble settled nicely, making F5 a very balanced, even handed, gentle sounding set. It's a set I can put in, load up any music, and it'll just sound 'right' for hours on end, without trying to be different or wow.
That last bit is an underappreciated quality nowadays, in my opinion.
I think the presentation is super cohesive and natural. I was partially expecting a bass heavy iem but it's not heavy, it's just right, even for a basshead. The quantity and quality are right there, but once the whole high end settles in, they balance it out beautifully. I hear bass thump like I get from Z1R and even pretty close to my Indigo.
Once I'm 20 seconds in to the first song, I smile and always say "perfect". Cable rolling also fun, really enjoying the Penon Leo Plus with it (and my Indigo).