Fits. You have to cut alot of shit, but it fits. I modded my g3 with an mx518 sensor. Was tight but eventually it worked. Won ASUS 2K8 summer with that :D
Well its the same where it matters. Size wise its identical. The difference is only in the clips for the top shell. And considering ou have to cut a shit load of stuff to fit the 518 in, including some bits of the 518 main board, the differences dont really matter much.
Okay, since its your first time, I have to warn you, its a hell of a lot of work and fiddling to get everything right.
Best would be if you had a dremel.
If not, knives would have to suffice.
A chissel would be awesome to have.
Luckly for me i have a dremel and a swiss army knife with alot of things.
A drill bit to cu a new hole for the screw.
Some scrap plastic.
Epoxy 2 compount glue. This allows you to sitck stuff that isnt exactly a perfect fit. Plus this can fill gaps and what not.
Supeglue. This you need to stick plastic that actually fits together.
Now the best way of actually doing it.
Since the mx 518 logical board comes in two pieces, you have to first fit the board with switches.
As the wheel mechanism is the same on the logitech mx518, g1 g3 mx300 and logi wmo, you have to have that as your starting point. Its important to note, that the height of the board mounting has to be very exact, so that all the switches are exactly horizontal and that the wheel continues to register rotation. Perfect alignment can take a couple of hours to a couple of days to get right. Your aim here is to make sure that the buttons click properly, the wheel button clicks properly and the wheel registers rotation.
After you have chopped, filed and built with epoxy a resting place for the board, its time to fix it. Use parts from the doner mouse and stick the plastic nuts to the new mouse floor with epoxy or superglue. The plastic nuts are the bits where the holding screwes of the board go into.
Assemble the mouse together and check that everything works. Buttons click etc.
Now its time to put in the sensor board. You will immidiately notice that its far to large to fit in properly keeping the original top and bottom screw placement. This screw will have to move elsewhere, but thats a different story.
Now place the board as close as possible to the buttons board. You will see that the sensor hole dont match, so you need to drill or cut out a new hole for the sensor. trim both the case and board to insure a fit inside the case. Here its immportant to note, that when trimmingthe logi board, dont cut any connections. Only the silicone around them. Placement is not to critical here. Height can vary a bit, as well as exact position, since the sensor has lod bydefault of several millimitres, so itsdifficult to screw this up.
Fix the board to the chassis as with the button board.
Now on the gallery which i showed you i had not yet made a screw to close the two halves of the mouse together. I used a wire, but at a later date i updated thedesign. Heres what i did.
Take a PCI slot case bracket and make cut it so that its roughtly 2-3 cm long. make two holes at two ends. The diamitre should be big enough for the normal screw to screw into, but small enoughso that the thred catches the edges. Bend it in the middle, so that 1 hole can be fixed to the upper shell screw hole, and the lower hole faces towards the very end of the mouse. Drill a hole in the shell so that you can screw the halves together.
I will try to get you a picturelater on when i'm at home.
But before you start, note this: NOTHING FITS. absolutely nothing, and you will have to do a really big job to make sure everything works in the end.
I've got both IE3 and WMO, they have the same DPI (same °/cm), and are both more sensitive than my 400 dpi mice. Heck, they're even more sensitive than the DA @450 dpi, but I suspect the sensor doesn't give 450 dpi since my mx500 is more sensitive than my DA.