Rainboe,
Did a similar trial in the B742 ourselves. Took a bit to sort out at 10,000ft with excursions down to 5,000ft, but landed [we chose ditching in fact] sortof OK.
The B744 is a worry, but if you have it sorted in the brain, you can use the alternate flaps but trip the correct CB's as needed to control inboard/outboard movement. However, not something I'd like to try in a hurry!!
G'day