340's won't make him overspined at all. The chart shows 340's for 65 pounds at that arrow length. Only 5 pounds puts him in a different spine class! I always recommend going to the stiffer spine when you're hanging right on the edge like that.Even moresoif talking broadhead arrows. And, who knows? game4lunch justmight decide to crank up the draw weight for elk and moose.

For those 400's, it'd be fine to shorten them and use them for 3D.