You have to do a bit more than that to force LV to run certain vi's is certain threads. This is where "Threadconfig.vi" comes into its own.
vi.lib\utility\sysinfo\threadconfig.vi
It all gets a bit tricky from here on in as you need to manually manage what vi's are going into which execution systems and at what priorities. Most of what you need to know is in this thread (no pun intended...lol)
Loop Timing & Execution difference