No, not on the floor
Just the walls will be sufficent enough.
P.S.- Please do me a favor and for your next grow operation, pitch that mylar out, and buy a can of Flat White Latex Based paint(has to be latex). Much cheaper than mylar, and just as good.
Paint = 95% reflectivity, never dulls(should be cleaned and reapplied once every 1-2 years)
Mylar = 98% reflictivity, but loses that very quickly, should be replaced every 2-3 harvests(half a year to a year, depending on how much you use your light)