You're right to be concerned about keeping the weight down. In my experience the 1.70 falls between a 1.20 and a 1.50 in terms of power. I have one on a Pacific Aeromodels Clipped Wing Monocoupe and it's an almost perfect match for that airframe. I also had one on a Top Flite Beech Staggerwing but found it to be marginal on takeoff. Once in the air with the wheels up it was plenty, but taking off was a test of resolve. The radial weighs 21 ounces more than a Saito 1.25 but you also have to add in the weight of an exhaust ring and an onboard ignition system with battery pack. All up you're probably looking at an extra three pounds. That's a lot on a plane this size. I do agree with you about the radial sound though. Nothing like it. Here's a short video of mine running on the Monocoupe. http://www.rcuvideos.com/video/Monocoupe-Radial-wmv