Generally molded inserts don't help balance, cut standard foams are really light and consistent and molded foams are a little heavier but can last longer. The balance problems are usually because of the rubber.
Cut ofna orange foams work great. They only fit the carcass of the losi tire tho. The proline tires are slightly larger and the fit is to loose.
Contact cement works best to glue the foam together it makes a flexible seam.
They work well i use them on the tracks we run pink slicks on.