This is a significant variation to the regular East Face route that nets you a spectacular and seldom visited summit. The "Extra Credit Summit" is the southernmost summit of the second piece of the Fourth Flatiron, is is 100 feet south of and lower than Green Mountain Pinnacle.
On the Regular East Face route (second piece), as you enter the hanging garden, look left for a huge flake that you can (barely) squeeze behind. This spot is where the gully becomes hiking territory and then threads into a narrow chimney, and also is where the gully bends right. To squeeze behind the flake we had to take our packs off. Then follow an easy ledge out towards the east face and set a belay on a large boulder.
Climb out on the east face and head more or less straight up the face. It's easy slab climbing, but there are only 3-4 pro placements in 165 feet. At 165 feet you reach the top, but there are no anchors there. Continue 20 more feet until you reach the rappel anchor, which is a huge horn wrapped with a 20' piece of sling. You can also place a bomber #3 Camalot here for backup (when belaying).
Rap west from the sling(s). This rappel is quite awkward to start and overhanging. With a 50m rope, you can't reach the ground and will have to traverse into the deep crack to your north. A 60m route would probably make it to the ground.
The end of the 25m rappel is a deep notch separating the Extra Credit Summit from Green Mountain Pinnacle. If you do the regular East Face route you go through this notch so you rejoin this route here.
Light Flatiron rack, including a #3 Camalot. You will need a 20' piece of cord if the rap sling is missing.
The tricky rappel off the summit.