I never did try that. But I'm figuring out it needs a fairly big model (or several copies) to work properly and for the filament change time to be acceptable.

I never did try that. But I'm figuring out it needs a fairly big model (or several copies) to work properly and for the filament change time to be acceptable. All in all, other than completely changing filament after a specific layer, I don't see the shortcome outweighing the benefits. But in this case I've mentioned it becomes very handy. For instance, to print a PLA 1st layer for bead adhesion and then print ABS on top of it.