These were my instructions I posted quite a while back, it looks like the line you drew was right about where I cut:
I used the cut-off wheel & cut about a 1/4" strip from where the lense overlaps the black housing...in turn, peeling the cut edge of the lense as I went along, then cutting through the rest of the housing, prying (carefully)until they became separated. I removed the top rubber strip by dremeling the plastic welds before cutting.
Sooo...when I put the housings back together I had a nice channel to glue. I taped them w/ 2 pcs of tape & used JB Weld (I did one side & let it dry overnight, then flipped them over & did the other side...of course touching-up the tape spots too). I put the two parts of the JB Weld into a baggy (cut-off a good sized corner...like a piping bag (see your mom if you need help w/ this step )) I then squished both parts together until mixed, squeezed the mix into the corner of the bag & cut-off a very small bit of the tip. This allowed me to "pipe" the mixture into the channel between the two halves & it flowed very nicely. I am still going to smooth a little silicone over the welds, although they look too pretty to cover up .
