I just went thru this length thing but in the opposite direction. I took a slightly different approach I don’t know if this is right or wrong or if my stroke is right or wrong but it is where I’m at now. Not sure if the fact I’m paddling a tandem canoe as a solo with the seat moved to the center.
I had a 230cm paddle and was hitting the gunwales when my stroke felt correct and when I would force myself to miss them the stroke felt less shallow than what I like.
So I went out with my 230cm and a couple pieces of tape and marked the center and then marked 2 new centers when I shifted the paddle over to make it longer on the end I was using. Of course I was shifting back and forth but it was simulating the amount longer I needed the paddle. My paddle is a cheap two piece so I made an extension piece that clips in like the paddle goes together. I repositioned the hand grips and tried it out 260cm is my magic number. The extension works fine and you couldn’t tell it was now 3 pieces and the plan is to buy a better paddle next year and by then I will know what I think completely of the new length. If anything with the longer lever arm my blade area may need to be smaller. So far I don’t find it too large though.
It is simple to try out a shorter or longer length just shift the paddle off center.