F13,
No, it won't work for several reasons; 1) a standard 18 inch dish does NOT have a skew setting 2) The smaller reflective surface is NOT big enough to gather enough signal for TWO orbital slots 3) The the biggest reason the "Yoke adaptor" would take the LNBF's installed on it outside of the focal point of the Dish's Reflector.
Dish 500's can be found for little money.
John