Thanks.... really a nice job. My dock neighbors C27 modified his opening for a Yamaha 9.9... but he cut down also... I guess he wanted the hatch cover to function normally... which I think was a mistake.... because he can't get the motor trimmed exactly vertical and that is way more important than the hatch cover.
I've wanted to upgrade my wonderful Tohatsu 2 stroke, but could never justify the change unless I could take advantage of a power trim feature. For all these years I've simply removed the cowling to kick the motor up into the opening and store with a canvas cover. Got so used to it that the modification went way down on the to do list.... but now you've inspired me with what I think is an excellent solution. I have a single backstay setup, so I considered bracing the chainplate with a horizontal piece that would distribute the load a bit.... However, with your somewhat arched cut I think that must not even be necessary.
My next task is to compare the Tohatsu and Yamaha's dimensions..... the Tohatsu would be my first choice if they are the same..... no slight to Yamaha, just my preference. Anyway, thanks a lot for posting your project.