(the feathers are RW, so they curve to the left, if looking from the rear).
If looking from the rear of the arrow they should curve to the right. Are you sure you got right wing feathers. The AZ ezfletch is right wing only.
I have use it before with feathers and they went on just fine. Insert the feather a little foward int he clamp and slide rearward till it stops. Doing this will get the feather a little tighter in the slots.