Time to cut the slot through the centre line of all the nose ribs but I don't have a dado saw so had think of a different solution. Looking around the workshop, the router seemed the best option and I already had an 8mm bit. 5/16" is 7.9mm so is close enough.
3/16" threaded rod holds th ribs together.
Built the jig out of scrap timber even down to retrieving plywood off cuts from the bin which raised the router bed the 1/4" needed to clear the tops of the nose ribs. The jig was screwed from beneath and the top. It isn’t pretty but worked well. Secured a routing fence to the side and routed 1/8" with each pass. 5 passes and the 5/8" deep slots were done.
