How young is to young?

Maybe the female will pass on her size, maybe she won't. Maybe her size is due to a recessive trait that will pop up later. Maybe it's not, and the male's size will have enough influence to prevent the babies from being small. It's not worth the risk to me.

If you want to breed tiny females, no one's going to stop you...I'm just saying that I wouldn't. In my opinion, there is too much risk of them passing on the trait--either overtly or covertly.
I also don't breed poor feeders, or aggressive snakes. I'm trying to improve the genetics in my collection, and those aren't traits I want to propagate, either. I don't think that small size is a desirable trait.

i would not start breeding until my female is around 2000 grams too be sure they can take on a breeding season with good success

You're probably best off purchasing females that are already over that weight, if that's your limit. A bit over half of my adult females have reached that size, but that leaves the rest of them between 1500 and 2000 grams. It's very common for female ball pythons to be lighter than 2000 grams as adults.

Be careful not to overfeed a female who SHOULD be 1500 grams until she is 2000, an obese female won't be a good breeder. They only snake I ever had slug out completely was a large female who put on about 300 grams too much weight going into the breeding season. She was overweight, and it had a bad impact.

Last season I paired my Mojave female. She was 2 years old and 1900 + grams. She did not take, never even built follicles.

This year she's about 2300 grams, and so far she is building nicely, but she's a hard breeder.

I would never start a female under 2 years old, no matter her weight. If she is at least 2 years old then I look at her size. Not just her weight, but her weight in proportion to her length, as well as muscle tone. If she is short and thick but with good muscle tone and is not fat, I would try her even if she were only 1200 grams. If she is long and skinny, around 1200 grams but looks like she could be much heavier, I would hesitate to try her, especially if she feeds well.

Gale

These are the weights an what year they hatched of my Females I bred this year
00 normal 3k plus grams empty
08 Pastel Female 1800 grams empty
08 cinnys 1400 grams empty, 1350 grams empty
08 normals 1700 grams, 1600 grams empty
09 nomal 1600 grams empty
09 het pied 1550 empty
10 pastel 1400 grams empty
10 cinny 1300 empty