The sgnature series was primarily designed for 6 cylinder aircraft motors, 230hp and up. The smallest they run is 70". The cypress was designed for the 4 cylinder aircraft. You can get them 66", 68", or 70". A friend of mine was running a 70" signature on his 180hp lycoming and was not really happy with the performance of it and when they came out with the cypress series Powershift swapped out his signature for a 68" cypress and gave him the difference in money back due to the cypress being $200 less. After running the cypress he is in love with it and about 6 of my freinds now run them on their 4 cylinders as well.
Larry