Here’s a guide to installing a flashlight on your SP-1.
Tools needed: 1/8 inch allen wrench, 5/64 inch allen wrench, and a flat object like a butter knife which is what I used.
Use the 1/8 allen wrench to remove the two screws to remove the small rail in front of the reg.
Use the 5/64 allen wrench to remove the small silver pin and then pull it free.
Now to remove the flashlight plug. You might be able to remove it with your fingers but if not use the butter knife to gently pop it out.
I use a Mini Maglite with an LED upgrade but I’m guessing any flashlight that same size will work. Both the twist cap and battery cap button versions will work. Now just put the rail back on (you don’t need the pin but keep track of it) and slide the flashlight in it’s space.
I'd wrap some tape around the flashlights handle to keep it in while shooting. It’s tight enough to just twist the light on and off for the twist type Maglights and with a few tries you should be able to click the light on and off without taking it out for the button version. If you want to give your gun that extra tactical look this is the way to do then buying a real tac light, it cost me around $15 for the light and the LED upgrade so it’s inexpensive. Another nifty little perk of having the light under the barrel is it gives your hand something to hold onto. So instead of using the forgrip/reg, the extension gives you a longer grip area to hold like a real rifle.
Here’s some pics of the light from behind the gun and to the side.