If you like to sail, many skills you learned on the 17 are immediately transferrable to the 28. The 28 would likely seem easier to sail because it isn''t as tender. The major difference is the mechanical devices between you and the sails:
winches and
wheels--and the momentum of the boat around docks. I moved from a 16'' Wayfarer to regularly chartering west coast cruisers over 30 feet. Between the two, was some training and courses, which if you do not have them, I strongly urge you to do because you are not alone out there and should know the Rules.
If you love to sail, I strongly recommend a coastal cruising course, and then just have at it. If it is about the cruising lifestyle and all the fun you can have by just being there, the selection of boats from 27 to 32 feet is huge and handling them is not alot different.
If you can charter a few big boats to get an idea of what it is that you and the Commodore are looking for, it could save you some grief in the long run. That''s what I did with no regrets.