Those flats "should" darken up a little, but may take a month. (Said Capt. Obvious.) But may retain too much brightness.
The Roto flats are not as bright as you might think. But I've had mine for a number of years. They were when new.
Other options might be:
La Bella Low Tension Flats. In some ways a little darker than the DTFs, but also a little tighter in the lows, to my ears anyway and I think they are the only thing on me that still works well. My last sets of DTFs seem to be warmer our of the package than they did years ago. May be due to their application as well. But always a worthy option.
I have tried the Roto NPS. They are definitely warmer than 66s. Enough that one would not know they are Rotos of any kind.
Fender makes a pure Nickle that really tames the lows. GHS as well.
Pyramid Gold Flats are about as warm as you can get in some ways. Maybe to much so.
Elixir NPS tone down the highs very well. Almost like a pure nickle string. Have some nice mids and not hallow sounding.
If the lightly used Fenders or Rotos are of interest (or both) DM and I'll gladly send them to you. I'm thinking both would be long enough. I have a set of uncut light Fender Nickles (.95) as well.
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