I was at an agility trial one time and there was a LARGE sheltie, my Aunt commented on how pretty her 'collie' was and the lady got upset, it was a sheltie, just extremely large. My cousin has a 5 month (?) old and he's already 14 inches tall

I think it has to do with BYBs. It's the same with JRTs, you see really itty bitty ones and then I have my ginormous monters

Sorry I can't really answer your question

Oh, I found this site, I can't really look through it since I need to get to class...but from the little I saw it looked pretty informative! Hope it helps.

http://bowlingsite.mcf.com/Size/size.html