i dont know where you heard that myth. i recently purchased a kyosho tiger moth and put an os .46ax in it mated with 11x6 prop. initially it came out a little tail heavy, but a 6v rx battery solved that problem. on the grass, the moth handles well at taxiing speeds. it actually floats in a little longer which makes it a little harder to control on landing with the rudder. after a couple landings, you do get used to it. take off with the 46ax is about 40 feet or so. i have found that the recommended aileron throws were way to little at only 10mm. it's more like 15-20mm to get any kind of roll. it flies around real slow with trainer like characteristics.

i had bought the tiger moth hoping it was a sport type plane, but it flies very scale. instead of sport, i have came to the conclusion that i have a dedicated sunday flier. your spit will be a much faster, sportier flyer than the tiger moth by far. if i had to do it all over again, i would put a larger 4 stroke in it. good luck