You shouldn't see any poundage increase with snakeskin backings. Like I said earlier, all it brings to the table is decoration and some water protection.

I haven't used baling twine (I assume you're talking about hemp twine!) as a bowstring in many years. If memory of things from more than 40 years back can still be relied on[:-], I was using a double strand of twine, twisted together and heavily waxed, for a 45 pound bow.