The problem is that Chinese missiles are generally bigger due to weakness in solid fuel technology, so the J-20 cannot carry as many AAMs as the F-22.
Interesting, can you send us some links (reliable ones) on your claim that Chinese missiles are bigger because of the weakness the Chinese faced in terms of solid fuel technology?
Also if you bother to do a little bit of research, you would actually find that the Chinese missiles are almost the same size as the US missiles, for example PL-12 is roughly the same size as AMRAAM.
Length: 3.85m
Diameter: 203mm
Weight: 180kg
Length: 3.7m
Diameter: 180mm
Weight: 152kg
The difference, I doubt will actually mean carrying a couple less missiles. And also... has the Chinese actually release any information on how many missiles J-20 can actually carry, or was it just an estimation of what we are seeing in a couple of picture?