Bad Idea ...

just use a voltage divider in the input ...

1/2 is the easiest to find ( 2 equal 1% resistors ) ...
2/3 is still easy ( 1 k and 2k resistors @ 1%)

Installing a load that can draw 300 - 400 mA on demand is rather a good thing ...

But think regulator doesn't output EXACT 5.000 v ... so measure it and enter value as a parameter for calculations ...

Alain