If your signal is weak enough on 110 and 119 that you cannot use a Dish500, you need two seperate dishes, not a make-shift dual lnb.
The 24 inch dish is not focused properly for 2 lnb's, it has a single focal point, whereas the Dish500 is designed with the horizonal focus longer than the vertical focus so the two lnb's are preferred.
You'll probably not get any stronger signal with 2 lnb's on the 24 incher than you did with the Dish500.