I am currently moving up the plan to maintenance so have done the 810 plan, i really enjoyed the 810 plan after doing SS/SS+ as i felt like I was eating but still dieting, i still had losses and used it to keep sane over xmas too!
Pretty much the same as SS+ but with extra milk and a larger portion of protein and another spoonful veg, i found I could split the portions to make 2 small meals and have some lunchtime if I wanted to. I don't think that Ketosis is sill maintained so it's possible to feel hungrier.
I think that with 810 and 1000 you will maintain ketosis - possibly even with 1200. I am currently doing ~1100 calories and the ketostix show me in ketosis.
In fact, when maintaining, I believe that your body may dip in and out of ketosis depending on your energy needs and your levels of glycogen.
It is my understanding that a thinner/leaner body has less of a glycogen store as the lean muscle is burning calories all the time. I think the figures are that for each pound of lean muscle you have, your body burns an extra (approx) 10 calories in a day. So, if you are carrying a few pounds of muscle you burn extra calories just by it being there! It's not a lot, but at least it is "helping" you maintain ....
That means that if you control your calorie intake, tone/build some muscle, and exercise to a moderate level, you can be in and out of ketosis even when eating "normally" .....