Mixing PB and 80/20 Strings?

[lpa53]

I have always preferred phosphor bronze strings (usually John Pearce) over 80/20s because I like a mellower sound. But on my Hoffman Jumbo, I've begun to hear the bass strings, especially the 6th, as a bit dull and thudding, without any ring at all. Some of this might be due to the original G7th capo I like but I want to stick with it.

Anyway ... this last string change, I added 80/20 6 and 5 string to PB on 1-4 and it sounds a bit more to my liking. My question is whether I'm fooling myself. This would possibly be the case if the trebles on 80/20s are the same composition as PBs. Is that the case, or are the trebles different? And ... are there other players out there who mix strings like this?