I have the SIC X-14 Pro 26" wide, and think maybe for flatwater you should consider that also (in fact didn't even know about the 28.5 wide version, I dont think we have seen it here in Aus). But if you are wedded to 28 wide then I 2nd the vote for SIC there are a great board and cut through the water, and love paddling mine, even surfed it in a bay wave the other day, when you get on the back it surfs unreal, and thats a big jump for me as i was wedded to 30" until a few months ago!
Let us know what you decide