Hey Davy it is very important to balance your props,you dont want any extra vibration be put through your model,
This vibration can rattle components off pc boards,like the ones in recivers,servos,crystals have seen it break off soldered joints.
Single cylinder engines can only be balanced so much and add a little vibration,also it can wreck the bearings in your engine,rattle screws,fasterners lose.
You dont need to buy a balance jig,I just mount a bit for round bar in the vice,must be level,slide prop mount hole over it,give it a spin,remove some material with sand paper,file.Give it another spin,End result is you want the prop to balance in a horizontal plane.