Michael:
Flexible props are commonly used on planes with no landing gear, and they do save money.

But flexible props, lacking rigidity, cannot be as efficient as a prop that holds its shape under all aeordynamic loads.

You don't need that higher efficiency.

And, being brutal about it, your trainer is not expected to last long enough for the vibration to damage it. Just a fact of (trainer) life.

When your skill advances to the point that a crash is a truly rare event you'll want to do everything to maximize airframe life. I have several flying planes more than ten years old, and two that are more than 40 years old. Pictureattached is about 15 years old, worn out two engines, now has its third.

So don't be overly concerned about prop balancing right now, but do keep it in mind for later.

Expect to hit your props?
. The flexible ones are tops.

Bill.