Another way to think about it, I always fletch them 4x90.  The reason is like a boat prop, evenly spaced. I have never seen a prop with blades spaced unevenly. I don't really think it matters much but that's my reason for 4x90. Iput as much helical as I can. To many years in the Navy I guess......

Missed the last part of the question.....

Use helical or off set... do not use straight fletch if you want to shoot broadheads.

I experimented with 4 fletch arrows a couple years ago, and am hooked. For one, I can get 2 fletches out of a single full length feather, and since I use natural turkey feathers, I want to get all I can out of them.

As far as set up, I use the 4-90 setup, ariented in an X and get perfect arrow flight. I have no issues with feathers being noisy in flight.

I like the looks of the arrows, and they fly great even with the big wide 2 blade Zwickey broadheads on them.I put as much helical as I can get on them as well.

Me too. I shoot 4-4" feathers with no problems.
I use the 75-105, left wing helical. Well, as much helical as you can get on a 4" feather :-)

I like them for two reasons; 1) I don't have to look down to nock an arrow and 2) the feathers never "hit" in the quiver lke the 5" higher profile do.

my reason for switching to 4x4x 90 was the same as autumnarcher.  I'm cheap and I can usually get 2 fletches out of 1 full length feather.   secondarily, I don't have to look to nock an arrow.  they are aligned as an x rather than a +

there was a long thread a while ago where dr. ashby and others were experimenting with noise reduction...will have to see if I can find it.

found it...man it'll take you a long time to read....   http://tradgang.com/noncgi/ultimatebb.php?ubb=get_topic;f=1;t=057257;p=1