The PVC blades have very little twist.
The root looks too thin or narrow or not wide enough.  Might make it start harder, loose some torque and power in low wind.

Might try another set of blades, the same on the outer 2/3rds, but 'bigger' on the inner 1/3rd.  I bet it helps an awful lot.
It's only 10% of the power, but I believe it is a lot of the low wind torque.
Plus it will make them stronger.
You should go out and make them right now.  Nice night for it.  LOL.