I've been trying everything in my UT. Yes, it's modified. Started with a Gut/poly. Went to Kevlar. Went to NXT. Tried a HEAD multi.
Against my better judgement, I went to a full bed of Yonex 18-gauge poly and took it down to 44lbs. It plays fantasitc....BUT....I just hate that I'm going to take it out the third or fourth week and its going to suck. I've heard good things about Confidential but it's still a poly and I cannot depend on the string endurance. UGH.
I've played my UT with a thin poly in the Mains (like Tier 1 Black Knight 1.18mm or Volkl Cyclone 18L - 1.15mm, etc) @ 46 lbs, and then a softer string in the Crosses (something like a Babolat Origin 1.25mm (or equivalent in another brand like Tecnifibre Mulifeel, Isospeed Cream 1.23mm, etc) @ 43 lbs; or Weiss Cannon Explosiv @ 46-48 lbs, or a Syn Gut in 1.25mm @ 48 lbs).
This seems to give a bit more life to the string, especially with something like Babolat Origin or WC Explosiv... as they don't go dead (or bag out) as quickly, and help the stringbed feel softer while adding some power.
I don't know if you've tried something like that... so hopefully, that helps.