Out of curiosity, how many layers for vertical walls and top, bottom layers are teams using? We have printed many HTD pulleys over the years in both nylon CF and PETG. With a .6mm nozzle and 5 to 6 top, bottom and vertical walls , they have held up. We go for a slight press fit. On thunder hex we print the thunder hex profile. Also when possible for the high torque applications, we extend a hub to give more surface area. Another problem with Nylon CF printed power transmission parts is moisture in the filament. With nylon 6, 6/66 or 66 any moisture will greatly decrease the material properties. Once wet nylon is difficult to dry. I usually dry at 165 F for 24 hours then into a dry box for printing. The difference in a dry printed pulley and a slightly wet one is significant. Another thing we are in the process of dialing in is printing high loaded parts in pure polycarbonate. Not a alloy of poly like Polymaker PClite. Printing Poly is very difficult. And almost impossible for larger parts with out some form of heated chamber. But, the parts are amazingly tough. Nylon CF has very high tensile strengh and stiffness. Poly is not as stiff but the surface hardness and toughness are better then Nylon CF. I wouldn’t give up on printed pulleys except for the very high torque and shock load applications. Those may need the metal. Look at your printing and design methods first before declaring that you have to put metal in the pulleys.