How about 90' sections
Riser ABB Vetco Bouyancy joints, 90 ft lengths x 21.25 in OD x .812 in wall thickness. Grade X-80 rated for 2,500 kips tension, with two 15K psi choke &
Block One appears to be the shallower area, with water depths of 1500 meters or about 4,200 feet.
4,200 feet divided by 90ft sections = about 47 sections, lets round up to 50 sections to make the math easy, even for me.
5 hours = 10 sections per hour or one every 6 minutes if the 5 hour figure is accurate.
Mongrel