Total posts : 45366
Rich, I am not Marshall but I will offer my comments. Though any metallic conductor will function as a ground radial, for the money you will be better off buying some #12 or #14 solid or insulated wire. The foil covered web wrapped wire will not be as good a conductor. Due the the skin effect the RF current will be on this outside metal. The foil is not very conductive and if the wrap wire is aluminum (don’t know if this is) it will not perform as well as copper.
The unshielded multiconductor wire should be OK for this use.
Though bigger is better the difference you will gain with #8 as compared to #12 or #14 wire is not worth the cost in my opinion.