Not sure about 10kw, but 5 would almost certainly work, or something close to that. We seriously considered doing 50kw, but it would have doubled the cost of the 2006 power upgrade to almost $700K, doubled the electric bill and moved the daytime 5.0 mv a whopping ten miles - ALL over Lake Ontario. Since there is no point on the Lake Ontario shore where 20kw WYSL doesn't deliver 5.0 m/v (city grade coverage) it would appear to be a waste.
Protection factors for co-channel AMs: recall 50kw WMEX Boston, operating at the time with, I think, TWO towers daytime - and 10kw WNLC New London with THREE - only 70 miles apart, both on 1510?? I think it was Dan Strassberg who pointed out the somewhat astonishing fact that WNLC's main daytime lobe was actually aimed at Boston!! Of course WNLC 1510 is gone now, but it's a fascinating piece of directional AM history.