Put them in that "groovy" spot....if that's where you want them! /forums/images/graemlins/rotfl.gif
Seriously, I think the question is how can you make a flat speaker fit on a "non flat" surface??? You will need to come up with a small plate that follows the door contour on one side, and has a flat speaker mouting surface on the other. You could make it out of wood, or plastic....whatever is easiest for you to "shape".
I could even see building up the groove with a few layers of mastic to make it flush....mount the speaker, and then trim off the excess, so it doesn't really even show.
Lots of ways....you just have to start thinking creatively. The main thing is to get it sealed well....the sound will be far better, than if you leave gaps around the speaker....