Here I’m instancing a group of Arnold standin sequences, and giving each instance a different start frame. (Each standin sequence is an animated bulge on a cylinder.)
PS It works fine until you go past the last frame of the sequence, because looping or clamping the ShapeInstanceTime doesn’t seem to prevent SItoA from loading the non-existent ass file.
eX-SI
ICE, scripting, and other tech stuff about Softimage aka XSI
eX-SI 
i was able to do this for sure on a ice instancing crowd system i made years ago. i wonder what changed to stop this from working?
the looping of ShapeInstanceTime i mean…
In brief, what happens is that even if you clamp (or loop) ShapeInstance to the range 0-20, when you go to a frame like frame 25, Softimage (SItoA?) tries to load the 0025 .asstoc and .ass files (and fails) and then falls back to loading the 0020 files.