ORIGINAL: Charlie P.
Great Planes offers the tail wire braces and anchors from the 27% Ultimate as a seperate item. (Tower # GPMA2844 $7.49). I've also used these to brace-up a Giant Super Sportster. Very easy to install and adjust.
I tried this on my Giant Super Sportster. The brass post that go in the horizontal stabilizer were not long enough in my case. I manage to make it work though by countersinking the top hole and gluing instead of using the retaining washer