MAG 3D to 4C. Has anyone here recently done this

I know this is a very basic mod(if that). I just put the Terralux EX into my 3D mag. I also replaced the lens with a UCL clear lens. I would like to put 4C batteries instead of the 3D. I have the PVC tube and will cut it to 7 inches. Will the flipped spring work for a good contact?
Will the extra presure from the longer batteries hurt the head unit?
How much brighter will it be and do I really shorten the usful life between battery changes.
I know at the point I am already up to 30 doallrs in the MAG parts and probably should have bought another light but I like the size of the MAG and I have had it since the eighties. Thank you.

isnt a 3D about as long as a 4C? So my question would be.. why would you want to?

I think the higher volts would give more light?

what's got higher volts? A 4C mag or a 3D mag with 4C's in it?

I want to run my 3D make with 4 C's to get the six volts for the terralux led.

C alkaline batteries only have about 1/2 the capacity of D alkalines, but at 1 Amp the C cells will still go for 3 hours or so. The gain in perceived brightness from the TerraLUX MiniStar 5 SSC P4 U bin drop in (what a mouthful ) will be about 22.5% if the manufacturer's claims of 100 lumens for 3 cells and 150 lumens for 4 cells can be believed (150 sounds a bit optimistic to me). I got this number by taking the square root of the lumens ratio - SQRT(150/100). This is Stephen's power law for light intensity.

The flipped spring should work for you. No damage to the switch assembly will result. I would change my 3D to 4C too if I were you.

I've done this with 2D mags running 3C cells inside them. I don't know about the terralux and what voltage it can support. If you go beyond what it can support it could fry the electronics or the LED.

When I've done it, I've made it permanent as the flipped spring can sometimes be a contact hit or miss. I dremeled the anodize to bare metal in the bottom of the tail cap, took the spring in vise with pliers and cut it, and re-bent it. Only a few turns were needed left of the spring. I pushed it down into the bottom of the tail cap, and it holds it'self in snugly. Then I used the PVC of course, with some paper wrapped around it to hold it in the body so it didn't fall out when changing batteries.

Thanks. Success. THe flashlight is noticable brighter. It was very easy. I wonder what I should do next?

Did the same thing but just rolled paper around it. Works well.