seanc56 wrote:What are the marks on the shaft under the pulley that looks like heat discoloration? Almost looks to me like you might have binding going on under load which would make the belts job that much harder.
Those caught my attention too. They line up with the sound insulation so it must be from contact with that. The smaller axles avoid this.
Regarding the 5mm pitch pulleys, they won't fit within the two inner layers of material and the bearings. [edit: They will fit. I didn't find hubless from my vendor, last time I looked.] However, they would be the next step if this gives me any trouble in the future. I would have to add another layer.