Updated timeline - the rats are good size. I have since switched to offering him small rats.

09/26/12 - 1379g
10/01/12 - Stool (which means he ate just before I got him)
10/13/12 - Stool
11/01/12 - Shed
12/18/13 - 1250g
01/14/13 - Took Med Rat
01/28/13 - Shed/Stool/1295g
01/31/13 - Took Med Rat
02/13/13 - Stool
03/21/13 - 1230g
04/04/13 - 1219g
04/16/13 - 1190g