Ben,
I don’t know if I should go with the oc 705 or the 703. The 705 as you mentioned absorbs 40% more of the 125 hz.
Either will work well enough. But 705 is a little better, and it's more stable and nicer to work with.
so I wouldn’t include that tin material
Correct.
I was thinking of building between 4 to 6 - 4x2 traps and did I want to double up the 2 inch OC 705/703 and make them 4 inches thick or just keep it at 2?
If you'll also use them for bass traps I'd make them four inches thick.
--Ethan