Breadboarding with Dominos

[Birdhunter]

I'm building a mantle, my first.

The horizontal facing board just under the shelf mantle itself is 12' by 72" and is made of doubled up select 1" X 6" pine boards glued together to be 1 1/2" thick.

I'm worried about this piece cupping over time and was thinking about adding breadboarding to each end using Domino tenons.

Question 1... is breadboarding necessary?

Question 2... what is the best way to use Tenons to attach the breadboard ends?

Thanks

 

[roblg3]

Typically the wider the board the more cupping you'll get.  That being said, 1X6 is usually fine.  I would expect cupping from boards over 6" but if you follow the "rules" and traded ends when joining you're less likely to get cupping.  If you  "flipped" the layer the board should be stabilized pulling against its self.
When I do breadboards I reference off the underside (nonface) so i get a flat bottom.  I like my breadboards proud though.  it's not important which "face" you reference from as long as the boards are same thickness there should be minimal sanding.