I just finished this yesterday. We used a dremmel cutoff wheel to split the lense in half as the first step. We tried to cut off the flnage with the dremmel but his didnt work to well. I then taped the lense over the opening and made a rough guide line leaving a bit of fat all around. I took a 3 inch belt sander and turned it upside down on the bench and with an 80 grit belt I very gradually followed my contour mark. The sander just kinda melts off a layer of plexi and I made small adjustments on the sander and peeled off the waste a little at a time. I used a box cutter to trim away the waste, and the sharp edge makes a good scraper to fine tune the profile and clean off the edges. I used a file also to smooth out any humps. It turned out that when I was done, I had removed the flange also. This is probably a slow way to go as it took me several hours on each lense, but going slow and making frequent fittings makes a nice job of it. Here is a picture I took yesterday.
wingtip lense
