I emailed Evertune asking for the new Comb and the Sustain. I think I should share their answer because it is official information:
"The new comb was created because some customers were experiencing buzzing issues, however the new comb presses the saddles together with more force which slightly improves sustain and resonance. It is possible to order the comb from us and install it on your guitar if you wish to do so. We do have installation instructions available here: https://www.evertune.com/resou…w_to_install_a_new_saddle
The only other thing you can try is to use lighter gauges. It seems that the resonance and sustain with floating saddles in general seems to be impacted with stiff strings, which is most apparent when playing notes high up the neck, as the shorter length of the string will make it very stiff. Using thinner gauges will make the strings less stiff and should help with the sustain.
Yes, all new guitars are now shipping with the new larger comb, we no longer produce the old comb anymore but you might still find it on some older guitars.