So that's my disclaimer. i think that if you want less rocker you pull in the sides, which pushes out the stems and flattens the rocker. let it out a little and you get more rocker. I would think you can only go an inch or so either way. And as in my case the angle of the cross section of the inwhale is affected so if you know you want more rocker then you change the bevel on your 'whales?
It depends on whether you want to just change it or actually design in a different rocker.
As Dave suggests, just pulling in or out on the sides will change the rocker, but it also changes the profile of the rest of the canoe.
If you want to maintain the same shape/profile on the rest of the canoe you will want to redraw the lines, putting in the rocker you want and making sure the rest of the canoe remains "fair".
I did this recently (2 years ago) on my current project, and even though I spent considerable time laying it out, it wasn't perfect, as I got a "corner" at one point on the center line on each end where the rocker curve isn't smooth. I didn't see it until the canoe was stripped up, so I shaved the strips as much as a I dared to minimize the "corner" and called it OK.
If I were to do it over, I would likely pay a/the designer to modify his design to assure I got smooth lines. There are software programs out there where one could do it redesgn yourself but I have little desire to do that, I'd rather be playing with the wood and with a computer.
thanks guys for the info. I will be speaking with the designer soon and will see what he can do. i know, i know....i "should" start with just the design i want to build, but there wasn't a reliable one available and i like to tinker too. I'll also use a freeware program i found called BearBoat Pro which may work it all out.