I am going to see my vet today for my pup's first visit. I asked him on the phone this week at what age he does the ear crop and he said between 9 and 15 pounds for pits.
I will ask him about your question, If I knew the weight it would help, but im leaving in a half hour.
I did some research on cropping and my vet and luckily he's one of the best in my state, and people travel from all over to have him work his magic on their pups.
my first pit had floppies so this time i wanted doritto ears like my 2nd.
I like both looks, but the crop gives the head a nice look. IMO
i'll post back later today.