I've heard of stunted snake growth happening during the first year of not being able to feed all that much. The article is on my other computer at the moment.
If you like I can direct you to 3 sites that list Jungles at the 4-6ft mark. I've heard more at the 6ft are though.
I hope some or any of this helps.
In regards to Jungles their size is actually 4-6 feet so if you have a male the size is ok. Usually if they've been mixed with something else either Jungle/Coastal or Diamond then they could get bigger up to 7-8 feet plus. It 'seems' to be ok/right for a male. My 2cents.