I have been thinking about this too... If you can't beat 'em, join 'em...
I have written down what HAs from 18-18, 15-21, 12-24 would look like, but I don't know what the successful HAs use. I figure you need at least 4 PD, and all the riding you can get. Is going up to 4 HA worth it or not? Converting 8 points of skills for a 15-24 build, sacrificing Ath and PS? Who needs Ath if you're on a horse?
I was also wondering if anyone was down-converting some attributes back into skills. 15-18 or 12-21 lets you have significant amounts of PS and even IF or shield if wanted, more of a hybrid.