making large letters

[Steve N]

Well because of the differing grain patterns that you can see in your pic, you are talking obvious definitions of where all the joints are if you stick with hardwoods, and stain them, that will all show. If you move to paint, you can cover that, but I still think a sheet good, MDF, Ply, or the like will be easier to make, and work with.

[Gary G™]

The big photo has the look of cypress.
If so, as Steve suggests, a better grain match is warranted.
$.02