With the proviso that n-back performance often improves over (at least) the first few weeks of daily training. So if Mark_Gomer & his friend start n-backing at about the same time they change sleep schedule, they might get a spurious improvement in n-back scores.
My friend and I are starting the Uberman sleep schedule (six 20-minute naps spread evenly throughout each day) tonight. Have other lesswrongians experimented with alternate sleep schedules? Are any of you qualified medical experts who can give input or advice? Success stories and failure stories would both be appreciated, and I'll keep you guys posted on our progress.