Yeast Stepping in Carboy

I make starters in 2000mL flasks. I feel it works well but have read/heard that its almost impossible to 'overpitch' and even with the starter I'm making from White Labs or Wyeast I might be getting to 100 - 150 billion cells.

For Ales this could be double and even more for lagers.

I know I could decant some of the wort in the flask and add more to give the yeast more fuel to step up, but in a 2000mL flask I don't think I can give it enough for the amount of yeast I have.

So here is my question...

Any reason I couldn't make my starter and then after 1-2 days, decant most of the wort, pour into my carboy and give it a larger concentration of wort to continue stepping up. Then on brew day, just siphon off most of the liquid from the starter in my carboy and rack my beer right in on top of the yeast slurry left behind?

Thoughts?

I posted a very similar post a few days ago ('yeast starter in primary?'). I want to hear why we are always told to make our starters in a flask/ growler instead of just making our 2-4 liter/quart starters in the sanitized primary and throwing our cooled wort on top of it. One dude, WBC, said that he does it all the time and it goes w/o a hitch. I'm going for it on my next batch.

You can definitely make a starter in your primary (especially if it is a glass carboy). The only issue is that you can't easily crash cool and decant the beer off the yeast like you can with a flask/jug.

I am curious how big the beer is that you are making? A 2L simple starter (i.e. no oxygenation, no stirring) will easily produce ideal pitching rates up to a 1.056 beer. I wouldn't even hesitate to use that volume in a 1.070 beer, if it were well oxygenated and the yeast was fresh.