Once again - thank you for all your replies...
Another thing - stocks perform far better than bonds over time, so why bother with a stocks/bonds split and reduce portfolio performance?
The quick answer is that stocks offer a rocky ride, but consistently prevail long term, whereas bonds offer a smoother ride at a lower return. Read Tyler's linked article for a more detailed review, however.
I'm 100% in stocks. Yes, it's painfull during a bear market year, but over the long term stocks win (beat bonds) hands down...
As am I. Like you, I only discovered MMM and started my journey last year, and I plan to keep my 100% AA for at least until the last few years of saving. It's even simpler than that, because I'm using Vanguard's LifeStrategy funds (so I'm technically what, 97% stocks?), which are global with heavy emphasis on US and UK.
Good luck, and like the very first response told you, don't worry about the 4% rule, especially not right now. I'm assuming it'll be a little while before you have to make sure your t's are crossed and your i's dotted on your withdrawal plan, so definitely don't lose sleep over it :)
I also like the idea of taking up a small time gig once I hit my 4% FI number, then subsidising maybe half or more of my expenses that way (putting me at 2%) for just a few years to mitigate sequence of returns risk, and of course, overall risk of retiring just before a recession. You can dip your toes in slowly, keeping an eye on your portfolio and the market before deciding when - if at all - you'd like to fully pull out of working. Personally, I think a part-time job could be quite enjoyable...