Start with PD-125 for the pad type. Work on the pad of the splitter which is triggering the HEAD of the input first. Always set your head settings first on Dual Piezo pads, because the RIM gain is affected by the basic sensitivity set on your HEAD.
Starting with the pad connected to the Head side of the splitter.
Sensitivity: Set the Sensitivity so that your hardest hits peak the velocity meter. If you peak your velocity meter on every average hit, lower the sensitivity for that is where your dynamics come in.
Threshold: Check your Threshold. Very lightly play the head and set the Threshold up a little at a time until your lightest hits(like you would hit a light drum roll) no longer are sensed. Now, lower the Threshold just enough so that your lightest hits are sensed: that helps to keep your drum sensitive, but less subject to false triggering or crosstalk. On a snare that is not attached to the rack I usually set Threshold to 0 or 2 and higher on toms.
ADVANCED TRIGGER SETTINGS
Rimshot Adjust and Rim Gain are your key adjustments for the pad connected to the RIM side of the splitter.
Rimshot Adjust: If you set Rimshot Adjust to 0, you will find that you get no RIM sound. If you hit the RIM pad, it will trigger the HEAD sound. If you raise the Rimshot Adjust all the way up and you will get inconsistent response on the Head pad, so somewhere between 1.5 and 4 will give you the right response on most pads. The most important thing is to get only HEAD sounds whenever you hit the HEAD pad and only RIM sounds when striking the RIM pad. Find the best result for your RIM by raising Rimshot Adjust from 0 until your RIM pad response is sufficient without triggering HEAD sounds.
Rim Gain: This is similar to the Sensitivity setting. On the RIM pad, adjust the Rim Gain so that the pad's velocity works similar to the HEAD pad. Your harder hits should just peak the velocity meter.
If necessary, fine tune the HEAD pad response.
Scan time: This should be raised from the factory default if the HEAD pad response is inconsistent on equal velocity hits. If you hit it at the same velocity several times and the velocity meter is all over the place (loud one hit, soft the next), raise the Scan Time.
Retrig Cancel and Mask time: Raise these, if a single strike produces double triggering. Mask Time is most useful for Kick triggers. Not only can you control errant double triggering this way, but mask time can be used on the kick drum to correct extra unintentional beater bounce.