Work well if you can get them pretty much straight off the flange and out ten inches or better? I built 2 1/8 x 30 x 4 inch headers, and they seem to work well but after reading ANDYF's response on another thread I wonder if there might be enough benefit to try a different tube size, like two inch with a 3 3/4 collector. Andy, or anyone else have back to back data to show the difference?
Here is a pic of my current tubes, and the new ones I could go almost exactly in line with exhaust flow at the flange, for an exit angle.

What I try to do is get 1 cyl volume before the first tangent
point.... the collectors should be in the range of 16" to 18"
but that is based on other factors also... like RPM.... the primary
length is also a important factor... if you want send me a PM and
I'll run you engine through my header program
EDIT
this is the set I built for my 405ci... this is a 3 step.. 1 7/8,
2, 2 1/8... this is a 4"collector and 16" long
EDIT
Remember that your starting from the valve.. not the edge of
the head so you have to add that in

I sure do wish you were closer Mr. P. I'd love a lesson on building headers! I always admire your work.

Mr P, i remember the day you posted that pic of those headers almost 10 years ago and was blown away

Those does look nice