I may be wrong, but I don't think you could do this in Labview or any programming language. Stop bits are a key part of making sure the two devices communicating know when a byte is finished and is done at the hardware level, if there was a way to manipulate the stop bit to be 1 or 0, the communications scheme would fall apart.
Likewise for a parity bit. Though you do have one choice. If you are trying to use parity in a 7-even-1 scheme where you are only sending 7 bit data, you could set up both devices to be 8-none-1 and manipulate the 8th bit to be whatever you want.
