Now we attach the lens to the front plate. I did it like this : - remove the Jelly from the lens, it detaches easily. what is left on that side of the lens is a plastic rim about the thickness of the frontal plate. perfect ! - take a washer with an inner diameter close to (but smaller than) the size of the rim and draw or scribe that circle. The washer enables you to center the circle nicely. - on the front plate, file out the square window until your hole is about round and of the drawn/scribed diameter. This should be smaller that the rim on the lens. - Now carefully sand the hole wider (I used a pen so the sand paper would sand a reasonably round hole) until it thightly fits that rim on the jelly(-less) lens - after a fit is reached, be sure to remove burrs and crumbs of plastic from the underside of the frontal plate. - clip and file off the extending bit of the lens floor plate.
For good measure, I glued the outside of the lens where you can see it is made out of two parts. it is important that no water enters the lens.