I would stay with the canvas and paint. They are more likely to behave the same as what you already have, tending to behave more like one entity rather than two.
I would think that if you scuff the area where the board will be attached, a bead of PLP along the top and bottom should do okay, maybe with pin nails or screws to attach. after cleaning up any squeeze out and letting it cure you could run a bead of paintable caulk along the joints. The PL2 and canvas should still stick to that, I would think.
How are you going to wrap the drip edge board around the front radius? Kerfs or will it be flexible enough to make the bend? I wonder if a piece of vinyl trim might be a better option.