Unless you somehow had your filter mounted up next to the header or block or something, I do not see how this device could have any "heat shielding" benefit at all. Hot air circulates all over under the hood.
However it may be quite beneficial as far as minimizing turbulence in the MAF on a short ram type setup.
I did testing with a cut up plastic milk jug with good results. Even though this thing is chromed, it still looks a little better than my milk jug did.