Here are a few pictures of my mast mounted instruments. I used the same brackets from Veloctek which I used to mount their compass. The brackets are very solid. As you see in the pictures I needed to add some stainless steel washers and longer fine thread bolts to attach the display board. The bracket attachment is a slug that slides in the bolt rope groove. I ended up removing some aluminum to widen the opening to allow the slugs to slide in the groove.

Brackets were on clearance at West Marine.