Use the Stopwatch program on the TIMY. The TIMY will send the same "time of day" data to Split Second regardless of the program.
Make sure that you disconnect the TIMY from the PC if you are going to do any editing on the TIMY as additional data will get sent to SST and possibly create duplicate times.
You can then use the TIMY and Split Second to operate in tandem. The time of day information is the same so the net times will be the same as well.