Mike, the client books a specific category/size with the Outfitter. The PH conducting the hunt locates the booked size. If it measures bigger than booked category, but the PH identified and instructed the client to shoot that croc, then client pays zero extra. If it measures smaller than booked category, but the PH identified and instructed the client to shoot that croc, then client have the option to pay zero for that croc if he is unhappy with it...because thats not whats been booked. So as Outfitter we rather aim top end size per category, so the client always stand to gain by it without extra cost.
Same principle is in place for Buffalo/Sable/Roan/Kudu and one could assume all trophy animals. The Professional Hunter's judgement as hunting guide should be based on enough experience to safely judge horn lengths.
For some clients size and horn lengths are crucial when trophy hunting, and for others a good representative trophy size specimen is all they prefer, and in 99% booked hunts, this is made clear by the client during email / whatsapp discussions leading up to Offer accepted by means of deposit payment.
I hope this help.
PS: regards to Patsy Hahn, we had great hunts together in Zambia