Are Kentish cobs the biggest ones? And if they're completely covered, my nuts are phil-berts?
Mine are small but well filled and they've started dropping off.

Sorry, I am serious, but it is hard to keep a straight face about nuts.
On thinking, the biggest difference between my small nuts and my neighbour's large nuts is that his are in a very damp location and mine in a sunny, dry one.
Possibly more water would help?