there is an orientation attribute-

Code:
	<Fixture menuname="Test RGB 1" uniqueid="XRF1" excelexportid="RFB1" pixelwidth="4" pixelheight="5" output="RGB" channelcount="60" orientation="TOPLEFT"/>
	<Fixture menuname="Test RGB 1b" uniqueid="XRV1" excelexportid="RFV1" pixelwidth="4" pixelheight="5" output="RGB" channelcount="60" orientation="BOTTOMLEFT"/>
can you try using the TOPLEFT or BOTTOMLEFT - see if this helps.