In resonse to the balancer finger tips are not acurate by any means. However you need to look at what are you balancing. A trainner being 3/4 of an inch off isnt going to make the plane uncontrolable to an experienced piliot who should maiden any new commers plane. However 1/4 of an inch on a Funtana 90 can either tame it or spice it up quite a bit. I balanced my F90 twice once on my finger tips and the second investing in a balancer. No regrets I found i was indeed off and needed to move my CG around. As for low wing planes being inverted to balence its just to make it eaiser and a bit more acurate. Having the fuse below the wing when balancing is recomended.