Go to GSEDIT (open from the Start Menu or through GigaStudio), open your instrument, and select one sample (you will need to do this for all samples). In the bottom-left part of the window, it will say Velocity. There is a visual representation of the splits. Simply adjust the split points or add your own by selecting if you want 2, 4, 8, or more splits. Save this to a new file. Remember to do this to all samples in the instrument you wish to adjust.