Redwood is not a wood I like to use.

It is very soft and splinters badly when machined because the early wood is extremely
soft and the late wood is comparatively hard. Not good for bead and cove if you choose to use it.

The softness of redwood does not support the fiberglass/epoxy surface well so it dents easily.

The very dark color get very hot in the summer sun and can cause damage to the glass/epoxy layer.

Other than that it's great!

Good for dark accent stripes.

If you want a beautiful dark color use western red cedar.
At the lumber yard look at the board ends and pull the ones that look like a chocolate bar.

I used to buy wrc from Cowls in North Amherst when I lived in Western Mass, but many local yards carry wrc since it's used as housing trim. Start by calling all your local yards instead of driving many miles. The hunt is on!

My two cents.

Rob