I don’t have a Assioma SHI spindle (at least yet) to measure but offer a visual comparison of the spindle from a pedal (PD-EH500) that should be compatible to “hack” vs a Shimano XTR trail spindle. The difference in where the threaded portion is from the “shoulder” of the spindle shows why the XTR pedals probably won’t work (and why the trail variant in the pic wouldn’t work as well). The possible hack pedal has threads on the middle third versus the crank end third. The XTR trail spindle in the pic below won’t even engage a single thread in the EH500 body.
Bottom image is the Favero SHI spindle from their site.
