i mostly breed ball pythons and sand boas.. but a "typical" first time breeding male ball python is around 1000 grams where typical females are 1200-1800 grams for their first breeding (usually at 2 years of age)..
that being said i produced a clutch of ball pythons last year from a male who was a whopping 226 grams.. he was 6 months old..
he was producing sperm plugs.. so i thought "why not".. he courted and courted and courted.. and finally managed to get the female gravid after 2 months.. she produced 6 eggs.. 5 of which were fertile and went on to produce healthy babies..
i have seen people breed yearling male corns.. yearling male sand boas.. yearling male almost everything.. just because males "sexual" maturity isnt dependant on its weight (like a female would be)
i dont see how attempting to breed a yearling MALE anything is harmful to its health.. the worst that can happen is NOTHING at all 
anyways.. just my 2 cents