I have also been spinning quite a bit recently using some lovely hand dyed tops I bought from ebay. I seem to be able to spin a single ply that is about 1 ply weight - i.e. when I Navaho ply it I get something lighter than UK 4 ply but heavier than 2-ply.
These skeins are Navaho plied to maintain the subtle random hand dying - standard ply-ing hand painted tops always blends everything together which I didn't want.