Would this be overstocking?

[Tropical]

4 platy
1 female bolivian ram
6 neon tetras
6 pygmy corys

In a 20 gallon long tank (30x13x13)? I have a great filter and do weekly 20% water changes.

If that would be overstocked, would a 29 gallon be ok?

 

[BigJim]

That looks fine for a 20L. I would say you're not even really pushing the limits.