Dear Sir, i hope following article may help.

i think there would be slight changes

If i understand you well than it should be changed. The conversion of DN to reflectance should be done primarily before the processing.

I contacted USGS about this. They replied, "The constants represent the number of possible bits in a resolution (8 bit = 256; 16 bit = 65536), so they shouldn't change."

Thanks you should perform and check it.

May be change