For signage loosening up the whole thing would improve legibility, and also make it easier to adjust those tough combinations. Just my opinion…

The overall looseness depends at what size/distance this needs to work.

Assuming this is fine in those terms, to me moving the "t" left a hair is all it needs.

hhp

Jacob, I think ‘ti’ pair is looking ok. ‘ec’ and ‘ep’ pairs look too close. Also, are you doing this to save space or you don't like the original kerning?

Hrant - Thanks for giving me the benefit of the doubt, but I think the loosening Bert suggested will help legibility in this instance; and reverting to the original metrics accomplished just that. But, to my strictly "graphic designer's" eye, the "Re" seems just a hair too loose, and the rhythm seems to break at the "io." Should I loosen the "ti" in this case? Or is there a better solution?

You should probably tighten the "Re" slightly, but the "t" still needs to be nudged left. In fact I just looked at the string "ntnoto" in MyFonts, and it seems that in all the cuts of Avenir the "t" sits too far to the right.

hhp

Agreed. Thank you.