Upgraded suspension components will help. On the '09 and up frames, the various braces are not needed, IMO. On the older frames, it doesn't hurt anything, though I never needed one on my '06 and never had a wobble at any speed. But, it was far from stock suspension as well. I can't prove this (I don't have a wind tunnel), but IMO, the Batwing fairing design makes the front end get "lighter" at high speeds because of the air flow (or lack thereof) characteristics...you're basically pushing a piece of plywood that's attached to the forks through the air. The RG fairing design is not as prone to this, again, IMO.
Improper alignment of rear wheel as it relates to the engine mounting can also deal fits.
If a person likes riding a HD agressively, I would strongly suggest upgrading the suspension. In 100% of the cases I know about, those who finally get around to doing so after spending $$$ on exhausts, bling, engine mods, etc, wish they had upgraded the suspension a LONG time ago. It is the most significant improvement you can make to a HD. It's the very first thing I did to my '11, even before changing exhaust/tune.
That's my opinion.