We made up this boom assembly for our 580SM Case, which extends out 6' from the face of the mount. We had a quick attach mount already & made the rest up in the shop, including the front face plate that the boom & gussets are welded to. The little nubs sticking up on top further back, provide some additional places to wrap a sling around to keep it from slipping, for heavier lifts when required. Tried it out today for the first & it seems to work pretty good.
Nice job... Looks handy
Looks pretty good. I think I would have fabbed the boom up on a plate and bolted it to the adapter. That way you could use it for other stuff in the future.