In this photo the motor switch is visible. It is attached to the left side of the barrel (to the left of 'NERF' text/logo), with a wire going up and connected to the battery.
The initial mod (link below title) was good in giving increased firepower and control; however it was found that the original power controls that were still used for the battery were very inconveniently located and made the gun difficult to operate while wasting more than necessary battery power. Namely, the trigger locks if the motor is switched off, and the motor switch is above and behind the trigger, on the side of the gun. This is generally not bad since it prevents jamming bullets when trying to press the trigger with the motor off; however I am not careless enough to do something like that so the lock enforcement is annoying (also, it would be nice to fire at lower power as the motors are slowing down, which is impossible with this design). Additionally, with the heavy 6V battery in place, actually reaching the switch (which has to be done using both hands) is annoying and takes time which is bad in battle. Even worse, this means that it is better timewise to leave the motor switched on constantly, which wastes battery and effectively alerts everyone around to your presence.
It seemed natural enough for me to use two hands to hold the gun, with the left hand to support the barrel, and right hand on the trigger. To combat the problems listed above in this mod I removed the annoying physical lock on the trigger, and added a soft pushbutton switch to the front of the gun where I could press it with my left hand. With this in place, I could rapidly turn on the motors only when necessary, and control the amount of firepower. This also implies that I could keep the motors off for a silent approach, and be able to fire quickly upon seeing someone, which is impossible with the original version.
Note that if you are going for the "sneak attack" as described above (turning on motors right before shooting), you should not add weight to the wheels as described in the original mod posting (link below title). Adding weight to the wheels gives them more momentum and allows for fast firing of many darts, but it takes longer for the wheels to get up to full speed thus giving you less immediate firepower in the "sneak attack" situation.
To do this mod, open up the gun, and on the side that does not have the battery holder the trigger will be attached. Under it you will see the power/safety switch, and two screws securing the lock mechanism onto it. Remove those two screws and the plastic lock mechanism, and now you don't have the annoying lock anymore.
For the switch, you may use your own switch or use one of the two pushbutton ones already in the gun (one is on the handle, below the locking mechanism; the other is where the top "access door" is to make sure it is locked). De-solder the switch from its position, then solder two long wires to where the switch was (basically extend the wires so you can move the switch outside of the gun). If you use a switch from inside the gun, make sure it is soldered properly - there are three leads, where the middle one is always used, while the ones on either side are respectively on when switch open, or on when switch closed. Use a voltmeter or connected batteries to test which leads to use, otherwise you will have an 'inverse pushbutton' switch. The switch in the handle is wired correctly for our purposes, while the switch on the top door is wired in reverse.
Next, extend the switch outside of the gun and attach it securely, then test that it works. That's it for this simple but convenient mod. To go above and beyond, one may put the power switch on the trigger itself - this should give the NERF Stampede a run for its money (at least until you run out of the grand total of 10 darts; but then again you could do top-loading).
In this photo the motor switch is visible. It is attached to the left side of the barrel (to the left of 'NERF' text/logo), with a wire going up and connected to the battery.