The space on the transom should be the same, or similar, on 208 as the 228, it's the same shaped hull. Or so I think.
What I _know_ is that there is a night and day difference between the 9x12 and 12x18 tabs on my 228. Might be particular to the part of the Pacific I'm in, but with the smaller tabs I was forced to back off the throttle on 95% of the swells we see. Every swell was go up 1/2 the way, back off the throttle, go over the top, get back on the throttle. On extremely flat days I could skip that but we rarely see those conditions.
With the bigger tabs, I push them down, get up to around 25mph, set the autopilot, and put my hands in my pockets. The bigger tabs make the boat roll over the top of the swell rather than launch off of it.
It is a night and day difference. 9x12 are way too small for the 228 and the 208, go look at Bennett's web site and they say for 9 inch deep tabs, you want an inch of width for each foot of length. 9x12 tabs are for a 12 foot boat, not a 20 or 22 foot boat.
I'm 100% certain that if I had not upgraded to the 12x18 tabs I would have gotten frustrated with my 228 and sold it. They make that much of a difference, I can't say that strongly enough. It's a completely different ride, so much better. You are losing out if you don't get the correctly sized tabs. If anyone doubts that, I'll happily take you out in my boat and show you, you'll be a believer after that.