I've decided on a new base growth rate approach and also a new and simplified version of the accelerated growth buff. This should simplify the growth system but still keep some of its previous depth.

No longer is growth increased if you're sitting or sleeping. So you shouldn't feel pressured into doing nothing to grow faster. This includes the sunstone bonus growth mechanic.

The bonus growth from the action of eating has been removed, and moved all eating growth bonuses into the accelerated growth buff.

Sunstones now just give you a flat 2x passive growth rate boost being near them. You no longer need to get the stacks maximized for optimum growth.

You can still grow faster by doing some tasks that reward you with Growth %.

You do not grow if you are starving.

Accelerated Growth buff stacks up to a max of 60 minutes.
Each bite of food will increase the stack count up to a maximum of 1 minute.

Tier 1 Food : 1.1x Growth for 1 minute per bite.
Tier 2 Food : 1.2x Growth for 1 minute per bite.
Tier 3 Food : 1.4x Growth for 1 minute per bite.
Tier 4 Food : 1.6x Growth for 1 minute per bite.
Tier 5 Food : 1.8x Growth for 1 minute per bite.
Tier 6 Food : 2x Growth for 1 minute per bite.

The base passive growth rate of creatures has been normalized and each size category of creature has a different growth rate.
To increase the rate of your growth you need to gain the Accelerated Growth buff.
You can double your passive growth rate by being near to sunstones.

(24 hours base to grow a huge creature)
15 hours, to Adult
6 hours, to Sub-Adult
3 hours, to Juvenile

(18 hours base to grow a large creature)
11.25 hours, to Adult
4.5 hours, to Sub-Adult
2.25 hours, to Juvenile

(12 hours base to grow a medium creature)
7.5 hours, to Adult
3 hours, to Sub-Adult
1.5 hours, to Juvenile

(10 hours base to grow an average creature)
5.625 hours, to Adult
2.5 hours, to Sub-Adult
1.25 hours, to Juvenile

(8 hours base to grow a small creature)
4.5 hours, to Adult
2 hours , to Sub-Adult
1 hours, to Juvenile

(6 hours base to grow a tiny creature)
3.375 hours, to Adult
1.5 hours, to Sub-Adult
0.75 hours, to Juvenile