I just put a Sunray seat on my RK. Like others have said, it seems to raise you up an inch or so judging by the windshield height. But I can still get my toes on the ground (30'' inseam).
I just got done with my first long ride on the Sunray and thought I'd share my thoughts on it. While the heat worked great, the comfort wasn't quite what I hoped. The shape of the seat is very similar to the Ultra's seat and I found that the well-padded but dished out rider's section basically forced me into a single position. It felt really cushy at first but tiring after a while because I couldn't shift around enough to change the pressure points. The stock RK seat is firmer but the rider's portion is a bit bigger and flatter so it's easy to shift around a bit as needed to keep the position fresh.
On the plus side, the Sunray's passenger section is huge (at the expense of the rider's area) so if you want to make your passenger happy, this would probably do the trick.