Hello 5.8 sailor,
Going from 8.5ft beam to 11ft beam is one big jump in hprsepower, like 29%. This also means the max loads in your boat are going up by 29%. As max righting moment goes up, so does sail force and sail cloth tension especially leech tension. Mast compression goes up. Main beam loads go up. Centerboard bending loads go up. Sheet loads go up. If all the forces acting on the boat didn't go up, then the boat wouldn't go any faster. There are no free lunches.
But, if you want to go faster, do it!
Bill