Matt: You might consider Dyform wire as an alternative. Less stretch than regular 1x19 wire and not much more cost. You can get rod rigging with the same end fittings as you have now (T-ball fittings in the mast and barrel turnbuckles on the chainplate ends). If you're contemplating rod you might find that you are better off with PBO. There is a nice chart comparing strength, weight, stretch and windage in this publication from Navtec. Go to:
http://www.navtec.net/manuals/NavtecBiConicPBO.pdf. If you're going to go part way might as well go all the way.
By the way, the Defender price for 316 Stainless 1x19 wire in the 3/16" size (the size of the uppers on a E32-2) is $2.09/ft ($3.43 from West Marine). Dyform 5mm (the equivalent size) is 2.69 from West Marine. Why the Dyform is cheaper at West Marine than their regular 1x19 wire I don't know. I do know that if you go outside of the normal marine channels for 316 Stainless 1x19 wire you can get it for significantly less than $2/ft. Mary and I installed a deck railing system a couple years ago using it. I used the excess for new lifelines for "Dark Star."
HAPPY NEW YEAR