I won't. Ergo..
I've more than enough experience with unexpectedly breaking glassware, and have the scars to prove it. It's a risk I WON'T take. It is much less painful to just wash a pot than pull shards of glass out of yourself, IMO.
You must have got a good deal, then. Amazon's price for a 5L beaker is $49.95 vs the $26.00, used, for a flask, on Ebay. Rebel Brewer's flask is $34.95, new. As I don't plan on boiling in it, (electric stove), boilovers are a moot point.
Try this: http://www.walmart.com/ip/Anchor-Hocking-Cracker-Jar-with-Lid/16520333. Using stepped starters, it should work fine. As for the volume question, no. You decant off the starter beer, retaining only the yeast. On the final starter, simply retain enough liquid to get the yeast back into...
I'm currently using a 1L flask and 1/2 gal. glass container for ale starters. I understand lager/pils need higher cell counts. What do you suggest for starter container size?
My first match was horrible; after two months it was barely tolerable. Much better quality ingredients, a larger knowledge base, and support forums such as this one, have greatly improved my brewing compared to when I initially started in the early '90s.
In the "before you begin.. minimum requirements" section of the recipe, it says, ".. or leave in primary an additional week." After that being said, it's your choice. Personally, after I pitch the yeast, I pitch the instructions. Advice from those here I'll trust much more than instructions.
I had a huge boiloff, ended up closer to soup than wort. Was cooled to 70° in 15 minutes. Topped off to 5 gal with cold spring water, pitched at 43°. Current results, at 63°:
To the many who have helped me improve here, I thank you.