>Anyone know the answer and where it is documented?

All the docs I need:

i=0
cAlias="Alias_7890"
DO while .t.
	i=(i+1)%10
	ci=Transform(i)
	cAlias=cAlias+ci
	Create Cursor (cAlias) (dum i)
	? Len(cAlias), Len(Alias())
	If not Lower(Alias())==Lower(cAlias)
		Cancel
	EndIf
endd

Works to a length of 254, breaks with "Invalid path or file name."