Ok i couldn't take a decent photo to explain what i'm on about, but i found a photo that makes things much easier to explain.
So what you should have already is the LED module from your ultra saber, something like this....
It seems to be the LED with a nut attached to the back (as a heatsink), most probably fastened with thermo paste.... the same stuff used to attach heatsinks to CPU's in a computer. Then once you've soldered the wires, the lens collimator (the reflective piece that directs the light) is glued in with a glue gun to the LED board. Then the whole thing is glued with a glue gun inside a piece of 1" poly c tube (the same stuff your blade is made from!)
Now, referring back to the first photo. See how the white PVC is a good size for a hilt but too loose for the 1" poly blade? This is why the Electrical conduit with an inner diameter of approx 1" is used to secure the blade. And because our LED module from UltraSabers is secured within an off cut of some 1" poly c blade, we can also slide the LED module right in there. Secure the LED module with either a screw going through the hilt, through the Electrical conduit and hard up against the LED module.... or just glue the LED module in there
Now the LED module is just over an inch long, and you want the blade to sit in the hilt at least an Inch and a half, thats why you need a piece of the Electrical Conduit approx 2.5" long..
I hope this is all making sense.. it makes sense in my head lol
Anyway i've drawn up a quick sketch in paint that i hope helps aswell.... feel free to ask if i've missed anything you wanted covered!