After doing some digging and going through, the refrence boooks I have on hand, I t apears that the only I 16 with 4 20mm cannons was the TsKB-12P a varient of the I 16 Type 10 and that it was basicaly a test bed.
Howeaver My other book, which is in storage Illuded to a type that was in service with a gunj package consisting of four 20mm cannons, regreatably I can not produce a more difinative explanation, But at present based on the material I have at hand I would say that the best armed/preformance model would most likely be the Type 27:
Two 20mm ShVAK cannons 150 rounds each.
TwoShKAS 7.62mm MG's 650 rounds each