Building a stand this weekend

[kacairns]

You could support it many different ways. Whatever you find suites you skill set for building and looks the best to you.

My recommendation based on what would look the best and in my opinion give best support for what you require would be to find very straight pieces of wood to make a knee brace out of, go full length with the pieces. Bevel the top end bottom edge of these pieces so they sit flush into the upright supports and to the top plate you intend to extend out. That will support the top plates the full length, give them the rigidness required to support and distribute the different stresses on the top plate you will be subjecting them to as you work.