Driving to the 5 level with the north hand is aggressive. Driving to the 5 level and then cuebidding 5D shows a lack of understanding of the auction, 5D just shows a hand that is better than a signoff in 5H. Since it would be impossible for north to drive to the 5 level with less, he should signoff in 5H. South could just bid keycard over 4S imo, 6 can never be bad opposite 3 keycards.