It's not the size of the tabs but how you use them in conjunction with the motor. Grady built that boat for 4 decades and I trust they know what they were doing in regards to the tabs. I have never had an issue running the boat now 13 years with the factory equipped tabs. Let us know how you like the bigger tabs.
Ps at the end of the day it's a 22 footer . The bracket doesn't add 2 feet of wetted hull length. It just doesn't.
You are correct that it doesn't add more hull because, well, there is no hull under the bracket. That wasn't my point. My point was that the bracket puts all the weight 2+ feet further back which is going to push the stern down more (just ask any 226 owner why they like their boat). With all that weight back there, the tabs need to work like they are on a bigger boat.
While I absolutely adore my 228, I've come to realize why Grady stopped making them. It was a great design for lighter 2 stroke engines, everything about that boat was pretty much perfect when you had a light engine. When they plopped a heavy 4 stroke engine they really needed to redo the molds, they should have raised the deck and they should have gone to a bracket with more volume in it (that would have made it more like a bigger hull) to lift the stern. They didn't and the 4 stroke 228s are not as good as they could be.
I'll report back on the bigger tabs. The reason I got them is because one of my fishing friends used to fish in the Pacific on an 18 foot Grady center console and he got on my boat and said "My 18 foot boat ran way better than your boat does". He went looking for what I could do to fix my ride and after looking at my prop and tabs, he said "bigger tabs".
All of that happened because I fear swells and he asked why that was (his current boat is a Canyon 271, he puts that on autopilot and comes home at 25-30 knots through swells and doesn't touch the throttle). The swells launch my boat so I have to go up the swell, get about halfway up, pull the boat off plane, ok, over the top, goose it, repeat.