Here's my report on caponizing the White Leghorn rooster today.
He did seem to move around more that the others. I use a pair of square plastic bottles that alcohol comes in for traction weights. It makes it easy to adjust the weight for the bird. I tie a cords around the bottle necks and loop the other ends around the wings and feet and let the weights hang off of my table. For the first one I did, a 5 week old EE, I filled the bottles 1/4 full or only about 1/2 pound and I was concerned that it stretched him out too much. He couldn't move at all. The older EE, allegedly 8 weeks, probably much older, took a full bottle and it held him securely. I also used a full bottle for the WL today and it held o.k. but he was able to move a bit.
I paid more attention to how the testicle was attached and yes it was attached all along one side. I believe at least one of the other birds was similarly attached but the prior ones pulled free relatively easily. With the WL today, I got the snare around one end and worked it around until it went over the other end. I cinched it down and it gathered the connective tissue underneath. The difficulty was that as I tried to work it free it was not coming easily. Based on my earlier successes I was probably overly confident and pulled too aggressively and did not twist as I did with the others which I believe helps with bleeders. I did both sides and both came out intact. I think it would have been better if he had been younger. He is recovering now.
BTW, the testes were about 20-22 mm long.