I put Chromes on my L-2500 a couple of years ago specifically to tame some of the harshness. Lowering the treble does help with that but, in my opinion, the L-xxxx's sound a lot better with less of the treble rolled off. I found the Chromes took off enough edge that I can keep the treble up higher where I like it and, since doing that, I've liked that bass more and more. Even with the flats on it, it still sounds great in general and it's still a fantastic bass for rock.
I've only ever put Labella DTFs on my Precision V, mostly as an experiment to see if they're really as thumpy and thuddy as the impression I got from TB. I was surprised that they have more mids and highs than I expected and I've liked them a lot, although I wasn't sure how they'd work on bass like my L. Then last fall I got to try a my old Warwick FNA Jazzman that I sold to a friend several years ago. He had recently replaced the Sunbeams he always used with a set of Labella DTFs and I was really surprised at how good they sounded on such an aggressive sounding bass. That made me consider trying them on my L-2500 when it's time to replace the Chromes but, since the Chromes are so perfectly broken in right now, that might not be for another few years.
Bottom line, I've been *really* happy with the Chromes on my L-2500 but would still be interested in hearing about someone's experience with Labella DTFs on an L.