Joe:
I don't think you'll have any problem "holding up" since there isn't much abrasion to worry about. Since you'll be covering it with glass and epoxy the strength will lie there anyway. Many use hardwoods since they like the alternating color scheme for the coaming lip. Also when using darker woods next to light, any gaps filled with epoxy are less noticable. This was very advantageous when it came to joining the deck to the hull. The deck shear strip I made was walnut and when joined to the cedar shear of the hull, the small gaps were hardly visible.

A last thing to consider is the lip. Is 9/16 enough to keep the skirt from coming off under extra stress? Most recommend the lip to be 3/4" to even up to 1". When you start to round the coaming lip with a half inch radius (the thickness of the lip)there isn't much flat area on the bottom of the lip to hold on to (1/8 to 1/4). You might want to add another couple 1/16" strips on or don't fully radius the coaming lip.

DAVE