Arcubalista: Geezer here.
Todd enjoys a very good reputation as a crossbow maker. I have no doubt his bows work very well, If he's making square sockets with nut suspended over-top on an axle, he's probably using a pretty strong axle and a fairly light prod. Even so, such a system will inevitably wear a bit faster than nut in tight-socket.
As for the socket itself, you don't want a half-diameter hole, you want a 2/3 hole. Less than that gives you too little mass around the top of the socket (Payne-Gallwey suggests a 5/8 diameter hole. That works okay if you reinforce the edges of the socket, otherwise, I recommend 2/3) a 3/4 diameter hole will sink the nut so deeply, you will HAVE to insert/remove the nut through the side, rather than the top, as can be done with 2/3 or less. As long as you have enough of a lug sticking out the top to catch the string, 3/4 will work fine, it's just an assembly/disassembly problem.