I like my oars to overlap by 6 in., especially in narrow boats. But then I do row nor'east coast style. Try crossing your legs opposite the oar arms crossing way, that evens the power level, then a foot board at full leg length. On each stroke my butt raises off the seat by 3 in., then settles at strokes end. If i don't get that lift, the blades are too small, or the length too short. When correct, I could maintain a comfy gps 3 -4 mph in my earlier 16 ft lapstrake across Fern ridge, on a great sunny morning, about like a 3 hp outboard.
Row like a dory fisherman 5 miles off Dover, with a catch to deliver, you'll love it. You'll have to try the latest oars, soon as I can let go the electric fun stuff, bigger boat with locks further aft, no idea on that setup yet.
Best wishes, Cal