Modelsim & VHDL Configuration

I am using Entity-Architecture Pair Configuration instead of Lower-Level Configuration, so that I can decribe two architectures for the same entity in a single VHDL file, and then use Entity-Architecture Pair Configuration to configurate the entity in the upper-level VHDL file.

configuration con of FREQMeasure_SingleChannel is
	for rtl 
		for U1: FREQMeasure_PeriodCounterDuringStrobe USE ENTITY WORK.FREQMeasure_PeriodCounterDuringStrobe(WithStrobeOutput);
		end for;
		for U2: FREQMeasure_PeriodCounterDuringStrobe USE ENTITY WORK.FREQMeasure_PeriodCounterDuringStrobe(WithoutStrobeOutput);
		end for;	
	end for;
end con;