I'm also in the midst of this project. I'm using some different materials
partially due to expense but also availability and quality. Our local
Woodcraft had some nice Padauk so the field it that and maple. I also was
warned by a friend to make sure I veneered both sides to prevent warping.
As somewhat of a novice for "fine" woodworking, I can't tell similar
density from a hole in the ground so I opted to do what Marks did and use
the same material on both sides of the substrate. Instead of apple plywood,
I just used 1/2 MDF, This seems to be working so far. My one problem was
that I don't have a drum sander and I was afraid to put such thin veneers
through the planer by themselves to I laminated them on both sides of the
MDF and when they were dry, I jointed one side of each and then put them
all through the planer. This actually worked quite well although it's
obvious from a cross section that the veneer thicknesses vary a bit. I'm
keeping my fingers crossed that this won't affect the warping issue.