Thanks. Any numbers? I was under impression only like 5% of light in a tent was reflected. And that just as distance reduced light reflection reduced it quite a bit. But then I get a lot of that stuff mixed up. My mind doesn't keep facts straight like it used too.
I guess I knew I wasn't gonna get away with a shortcut. :(
Here are lux readings using the Mylar 1mil blankets from Amazon... These blankets are nice cause they are really tall 84 inches and 54 inches wide so they cover the whole wall almost. I put the 5mil panda on the floor, it can handle abuse.
This is under some Gavita DE's cranked to 1150
Directly under light the reading is 33,600 lux
Next to Mylar is 21,200 lux
Next to some wood to block the Mylar (just for test/illustration): 11,100 lux
So at the point of measurement near the reflective surface is double some surface with poor reflection. So yes it is important if you want max efficiency.