Discus Growth Rates?

[Surferdave]

For a lot of us newbies, it's hard to tell if our Discus are growing at a good rate. I know it's relative to the strain and genetics but can someone provide a general idea of how large discus should be at certain ages?

2 months, 4 months, 6 months, 8 months etc.

I guess it's the fear of having a tank full of stunted fish.

Thanks!

Dave