I have one girl who is about 6 3/4 inches...but she's two years old. She's a tank tho...fat and a huge tail. She probably weighs a good 45 grams on that small frame... She did breed when she was younger due to a mistake on my part. She kept her first clutch for about a month and a half before she laid the eggs. After that she layed every month. She's developing eggs again. =/
She hasn't been bred again yet.
As for my other leos...one is a baby I hatched about 2 weeks ago. She came from the biggest egg in my incubator! But she's half the size of the albino I hatched two nights ago. O_O!
Another I hatched last year, she's 10 months old and probably only around 5 and 1/2 inches long...I need to find a ruler... She's still a little scrawny, and her siblings really outgrew her, but she's my little girl. I don't think I'll ever breed her...unless she hits some ~huge~ growth spurt in the next year O_o
I would think if they're smaller than that 6 and 1/2 inches there's too much of a risk. If they're still on that kinda end rate (like yours) as long as they're fat there shouldn't be too much of a problem if they're over a year. I'd say 2 years to be safe at least.
But I'm still a beginner at this tho. Hopefully someone more experienced will shed some more light on this?