You should try stacking the fibers, Steve. Then all you'll have to do is trim the top and bottom.
Here's a quick tutorial I did for a friend a few years back. Sorry for the bad pics.
First you tie in the tail, I usually do two on top for this. Spacing the stacks slightly.
The next step is to tie in the bottom. And easy way to do this is to split the fibers into two halves. You can do this by wrapping the thread and tying it in (just loop the fibers around the thread). You won't need as much fibers on the bottom because it is essentially doubled.
Tying it in..
Splitting for each side...
Pull it back nice and firm to get it to pull tight on the sides. You don't want it to flare out. Tie it right against the base of the top stack.
Tie in a top stack now, leave around a 1/16th to 1/8th gap. It depends on how big the hook and finished fly will be.
Here I'm holding up the top stacks to let you know how I'm working it forward. See the space in between the stacks.
Finished fly..
I tie these in sizes from 1" to 11" From size 10 hooks to 10/0. In a myriad of colors. Hope this helps you a little. Tying them can be VERY boring if you're tying dozens. But, they can be very effective at times.