A helical is the same no matter how much of the vane you see wrapping around the shaft.

Although you don't appear to get as much helical with blazers the simple fact is you don't get as much offset either, and you don't need to. The principle behind the blazer is angle-of-approach, and material stiffness, which compensates for it's short length. Sothe right helical that you use for 4" vanes will work as well with 2" blazers.

As an old troubleshooter from my telecom days, I have to ask if you have eliminated every other cause for the planing except for the blazers?

Does the exact same arrow with the exact same broadhead fly without planing with 4" vanes or feathers? If it does then try a more aggressive offset or a helical with the blazers. If it does not - well then you got other problems.