Well, as it turns out, after sitting on a buttercream frosting cake for a day or two, the royal icing flowers soften up enough to be pretty good on the cakes.
I have royal icing flowers on a chocolate fudge icing - made with butter, not shortening. At first they were too hard, but now, two days later, I am enjoying them along with the rest of the icing. I bet flavoring the royal would help, too. I'm going to try that next time.