I'll assume your 55 mph comment is a legal disclaimer.
The fact that you could increase throttle (especially without going to an easier gear) suggests the jetting is not too lean.
Generally with a lean surge on the main jets, the only solution is to slow down. If thats what you meant, then yes try one size larger jets on each primary.
If its the other scenario (not jets) then it seems that its the overlap from idle/transition to mains that could use some fattening.
and/or possibly a hair less timing at that rpm.
Since there is a little hesitation from stop, maybe the first experiment is to slightly richen and possibly extend the idle/transition mix. For that I'd start with trying slightly more restricted idle air bleeds. See how that works, especially for the off idle hesitation.
