Scott,
The answer depends on if you've already bought lnb's/switches already. The least amount of cabling would be achieved by hooking a Dish Pro Plus Twin lnb on your dish 500 (that pulls in 119 and 100 orbitals), then connecting a single lnb to the second dish (the one that points at the 61.5 location). This install allows you to actually connect the two dishes to each other, the 61.5 feed goes into the dpptwin lnb on the 'lnb in' port. This makes it so that a single line can be run from the dish to the receiver, avoiding an external switch in addition to the lnb. Hope that made sense..