Garage Door - addendum
Ron,
At one point you mentioned that you thought poplar wood was a better choice for the replacement plank. I would disagree and would encourage you not to use poplar anywhere it will get wet. It is fine wood to do mill work with, but it is very prone to rot if it gets damp at all..
Have you decided to try to duplicate the raised panel appearance of the rest of the door on your replacement panel? I wouldn't, because I tend to agree with you, I think a flat board installed at that height, painted white won't even be noticed. Where as if you try to duplicate the raised panel look, it will draw the eye to the obvious difference.
I do believe you are on the right track..
Roger