I am switching from 4" vanes to blazers and was going to put them on with the left wing helical fletcher that I have from my traditional days. Will this really cause the field tips/broad heads to unscrew? I also have a straight clamp but was wanting to put them on helical for better arrow flight.

Use the straight clamp at a 2 to 3 degree offset.The vane is so small you cant get much Helical anyways.I personally never had a tip unscrew on me either way.

I find you can get a good helical with Blazers. I have a friend that uses a left helical. He puts a small piece of teflon tape on his heads and they have never come loose. The weight,( or lack of), isn't an issue.
Here are some arrows I made over this past weekend. You can see the helical on the Blazers. BTW, I used a Bitz.

Try putting some string wax on the threads. That should keep your heads from coming loose. Left helical should be fine. Throw in an offset, you don't get much helical with the short vanes.

I fletch my blazers with my helical clamp and they work great. There is no way that arrow will spin fast enough to actually unscrew the head.

What Mike said. When I first started fletching years ago I was told to fletch left helical becasue I shoot right handed. That is what I did and still use the left hand clamp as I don't want to spend $30 for a new clamp. My brother shoots right helical and my tips don't unscrew any worse than his do.

I use Blazer's and fletch helical. It takes some adjusting but you can get a fair twist on them. Mine look similar to Txjourneyman's.