I have a chance to buy a brand new never flown Filton Element 170 for $100. I dont fly any competition just sport. Biggest engines I have is a four stroke Saito 125 or a 30cc gas engine. Will either or both these be suitable for owering this plane in a sport situation only.

Hi Jim,
Short answer: SAITO 125 - no way; 30 cc gasser yes! Long answer: current pattern set-ups have a thrust to weight ratio of around 2.4 to 2.6 to 1. You don't need that much power, but I would recommend a thrust to weight ratio of at least 1.5 to 1. I don't know much about gas engines other than the OS 33GT, but if you can get at least 7,000 rpm on a 19x8 or 20x6 prop you will have good aerobatic performance capability. An underpowered pattern ship is really not much fun to fly.
I have a 78" Extreme Flight Extra which is pretty much current pattern plane size. It weighs about 12 pounds and is powered by a piped OS 1.60 turning an APC 19x8 at around 8300-8400 rpm which is slightly more than a 2:1 thrust to weight ratio and it flies like a pattern plane. I am assuming your gas engine would just be muffled and your Element really shouldn't end up weighing much more than 11 pounds.
Good Luck,
Will

Gasser with muffler it is then. Cant wait to try it. Thanks a lot,