No the blades don't need to be inline with the fletching.
I won't start a debate on fixed or mechanical heads. But, will say I've been using NAP Spitfire Pro Series 100gr. for four years. They fly almost exactly the same as my field tips out to 50yrds. (I'll shoot 30yrds on game aminals)
Muzzys and Thunder Heads are both very good. I've found heads with shorter furrels are less prone to plaining off a faster bow.
The solid two blades popular with traditional bows don't do well a high speed.
Bow tuning is much more a factor in the arrows flight, so don't just focus on the arrow. As of late you see alot of guys going to light arrows. I'd stay up toward a 500gr (total) arrow weight, especially if you use a mech-head.
Switching from a recurve to a compound is like switching from a shougun to a rifle. If that makes sence to you. Shooting form is very differnt in the two.
Good luck. Hope that helps.
Another thing you should consider is a mechanical release and a peep sight or at least a kisser button, since you won't have your familiar anchor point.
Okay,you could still shoot fingers.
[This message has been edited by scout (edited 09-26-2001).]