I'm guess I'm a hoarder. I have two Ultra 24's and two Ultra 26's. I agree with Jay. The Ultra's improved the handling of my x-18. I also have a Solas 21. I like the Solas alot, but the Ultra's provide more bow lift and just feel looser. I will say the Solas does not blow out and provides unbelievable grip. But I have only blown out the Ultra, when taking a very sharp turn at high speed. the Ultra 24, 26 and Solas 21 all provided about the same top speed.
1978 X-18, SBC, Volvo 280T
Big Grizzly 21 Solas Prop
Heart Bay, Lake George, NY