6'3" is not " too deep" for the
ICW, but you will certainly have to watch the tide in areas.
Most of the US
east coast can be done in
offshore hops.
You can get the "Waterway Guide" which will list problem areas.
Summertime is mostly mild
weather and sea conditions.
I have done the US
east coast both on the ICW and
offshore, with a 6'3"
draft.
I did run aground in a few areas in the ICW.
Much prefer the offshore
route.
In the US you can buy a subscription to BoatUS or Seatow for about $150 a year, and they will come assist you if you run aground.