Most slicers have a "slowdown if layer time less than x" setting too...in Slic3r it is in the filament>cooling tab. That is typically a better solution...but i

Most slicers have a "slowdown if layer time less than x" setting too...in Slic3r it is in the filament>cooling tab. That is typically a better solution...but in this case I suspect this machine will have issues running slow..so the best bet is to only print large items.