If anyone needs to do this I believe I've got it working. I've added a new entry to the Linker Control File after the last GROUP entry in the ram section, like this:
GROUP :
{
__HEAP_START = .;
_heap_addr = __HEAP_START;
// __HEAP_END = __HEAP_START + __heap_size; /* Prefer not to spec the size */
} > ram
It was important to find the name "_heap_addr" as the value to be set, but once that was learned this seems to place the heap at the end of the specified data sections in the ram segment. Hope this helps!
~Tim