Alex:

If the core, the apron and the splines are all the
same wood, with the grain running in the same
direction then wood movement will not be a problem.

Me, I like to have options. Say I should have enough
rosewood or black walnut to replace the front and
back aprons bestowed upon me . . .

OH - this is probably obvious but I'll point it
out anyway
The dogs in the apron point towards the end/
tail vise
The dog in the moveable jaw of the end/tail vise
points towards the bench.
I ALMOST cut them all in the same direction.

If you have a face vise, either use the arpon as
the inside jaw, or if you go with a separate wood
for the inside jaw inset it so the outside face
lines up with the outside face of the apron.

Some round dogholes in the face of the apron,
two or three threaded, come in real handy
for face clamping, board support for planing,
a place to hold stock for sawing dovetails,....

http://home.comcast.net/~charliebcz/...CBbench35.html

charlie b