Unfortunately I have no first-hand experience with theses kits. After taking a look at their site, it looks like they addressed the trail issue; apparently they are using raked cups to overcome the trail decrease caused by the raked trees. Your question "wouldn't that create a pretty bad chopper flop in the steering?" is a good question. All front ends suffer from some degree of flop, but a well-designed and well tuned front end isn't going to give you any flop problems. My suggestion- go to http://www.chopperhandbook.com/rockers.htm
and read the section on flop. Then, contact AME if possible and make sure you know what you are getting into.
Also, take a hard look at the bike pics that have the front ends installed- compare them to bikes that carry the rake in their necks. Make sure the "look" you want can be accomplished with the rake in the front end instead of the frame. Everyone has an opinion, and personally the raked front ends "look" to me kinda... well... like a shortcut. Good luck, let us know what you find out. And post the pics!