hey-
I must admit, I absolutely hate the idea of a 1 screw tone bar- yes it gives you more pop or flex in the tine which can result in a better sounding note, not nescesarily sustain but a note with more punch. I have rarely met a Fender Rhodes I could not get the same if not more out of with 2 screws than a one screw job.
It all comes down to proper escapement and strike line adjustment, if you have both of these set and you have voiced the note properly- you will have your note loud and clear with sustain, as long as the tine is good and tight with the tone bar.
I am dumbfounded that the new Rhodes MK7 would use this Mk2 method. You cannot voice these notes to save your life. I know Fred at Vintage Vibe when he comes across this style, he will re drill the harp for the second screw.
You can also use tone bar clips which can be very effective-http://www.vintagevibe.com/p-295-rhodes-piano-tone-bar-clips.aspx
In the end, when you changed your grommets and screws, I feel you may not have set your escapement back correctly. Also, play with your strikeline and voicing. The piano is like a Rubik's cube puzzle until you shift everything in the right way your left with only a part of the puzzle solved.