I've worked with dozens of HS age players who have switched to LH with slapping during HS. Almost all hit at least .300 the first year but continued to improve significantly each year though out their career, eventually receiving all conference or all state recognition...a few even made it as D1 players. Speed, practice and parent/coach support are the key factors.
That's what makes me think it can't be harder. Yes, it's a TON of work and dedication, and I applaud those who have success. But it would seem like it would be easier to teach a right-hander to slap lefty than to hit ''normal'' lefty. But I don't know. ...
Also curious: How important is the speed for slappers at the highest levels? I see younger slappers who take advantage of the defenses' weaknesses. I'd think that at higher levels, the speed part is even more important because better defenses aren't going to mishandle as much. You're going to have to put more pressure w/ speed.