That's the thing I miss in all these guides. For me it might be possible to switch for weekdays, but the next weekend would desynchronize everything. Starting over by getting up on next Monday at 5 AM after few hours of sleep would make me give up. Knowing that I won't even give it a try.
I have been doing what the author describes for some time now (although I dont get up as early) and I find, that it works well to go to bed at any time on friday & saturday evenings as long as you give yourself enough time to sleep in as long as you want on the following day. On Sunday however, I will go to bed just as "early" as on e.g. Monday.
