Hi Pat,
I just went and checked, and I got the figure of less than 500cc's from Linda Weyand's research on the subject. I trust her and her sources very much, she's been a true data base of info for our email list. It's from Linda I learned about the 'floppy bag' syndrome, also, which is what happens when a pouch or neobladder is stretched all the time, and the reason there needs to be a limit to the amount of fluids between voids.
Linda answered a newcomer's question about the different diversions and I put a 'sticky' on it so that it stays at the top of the postings under the 'invasive' section. A quote,
"....the Indiana pouch and the neobladder have to be stretched to hold 400-500cc of urine so that you can go around 4 hours before needing to void....."
Take care,
Wendy