You can't, as far as I know. That is a very Windows-y way of doing things. And OS X doesn't seem to like Windows-y things.
I also never use full screen, not a single webpage is optimized for it and all it does is waste precious screen real estate for other things. Full screening everything is also very "typical windows user"-ish.
Since I've moved to OS X nearly 5 years ago, I realized that it's simply better to let safari choose it's correct size when pressing the + button than to try and have it take up the whole screen. I usually multi-task a lot so I usually have multiple windows open and stacked up and also use spaces a lot which I find much more efficient than having a bunch of tabs on the menu bar.
A typical(during university) usage patter for me would be 3 to 5 spaces being used, each with it's purpose. Say one space for Messages, FB and iTunes. One space for the study that's being done(texts, instructions, whatever), another space for actual work (word document, MATLAB, Maple). The other two will serve for looking up things on the internet as I go along.
Doing this in windows would be my taskbar would be filled to the brim with stuff and I'd have barely any way to know which is which with the tiny aero previews...