I think that compass rose is going to be tough to sandblast. How are you planning to do it?
I was thinking of blasting around that shape then adding a cnc cut alupanel or sintra compass rose on top which would either be painted or have vinyl applied to it. The east/west points would lap over/lay on top of the letters either side.
Get some chisels,,, 60 min tops it will be perfect.
I like that idea and I'm sure it would be satisfying to do and look excellent. I would like that part to overlap the letters so I' could build that part up from the wood surface....perhaps some easily carveable sign foam ... got lots of scraps of that around. I should mention that this sandblasted sign is only 15" tall x 42" long and the closest you could get to it would be about 16 feet away from the road (with a ditch between).