I'm a little confused on snake weights and what is "appropriate" or "right"....

I keep seeing posts that state every snake grows at its own rate, some will be long and thin, others short and chunky. At the same time, I keep seeing posts that say a snake that is such and such age should weight such and such and if it doesn't it underweight and/or not being fed right (either not often enough, not the right size prey, etc).

So what is or isn't right? Either there actually is a growth curve and snakes of such and such age SHOULD weight a certain amount, or there isn't and there's a wide range of variation. If there IS a growth curve and snakes of certain age should never be under a certain weight, what is that growth curve?

I want to take care of my snakes to the best of my ability. I am pleased with how they look and are growing, but according to some on this forum, my snakes are underweight. My snakes are eating every 4-5 days, prey of appropriate size according to what I've read on this forum (following the 10-15% body weight rule). So far have had no problem with regurge, and only refusal was my Mojo when he was in shed (everyone else has, so far, decided to eat while in shed!). Every snake has eaten their first meal within a week of arriving. But now I'm concerned I need to actually be feeding them MORE because they are "underweight", but at the same time I'm afraid of overfeeding them and having problems with regurge or refusals or what have you.

Mojo - Male hatched September 2012, acquired December 2012. Last weight 210g empty on 2/3 (up from 185g on 1/22).


Isabis - Female hatched August 2012, acquired December 2012. Last weight 270g empty on 2/3 (up from 220g on 1/22).


Cinny - Female hatched September 2012, acquired January 2013. Last weight 250g empty on 2/3 (up from 215g on 1/22).


Smaug - Male hatched August 2012, acquired January 2013. Was an assisted feed hatchling who didn't want to be a snake, now eating same size as everyone else on the same schedule, no questions asked. Last weight 200g empty on 2/6 (up from 145g on 1/22).


Thing One - Male hatched mid/late November 2012, acquired end of January 2013. I'd like to see him fatten up a little. Last weight was 60g empty on 1/23 (arrival date, shipped).


Thing Two - Female hatched mid/late November 2012, acquired end of January 2013. I'd like to see her fatten up a little. Last weight was 60g empty on 1/23 (arrival date, shipped).