If you cut between the frame doubler and the 3/8" hole the ratio is 1 : 10.
So if you remove 1/4" the rear of the fender will drop 10/4" (2 1/2")
On my bike I removed 5/32" for a 50/32" drop ( 1 9/16")
Put masking tape on the area where you want to make the cut.
With a sharp pencil draw a line square to the bottom edge of the tube.
Mark where the flat side area bends to form the top, where the factory weld for the doubler runs.
Drill a 3/32"pilot hole there. Mark the other sides the same way. 4 times total.
At the bottom of the tube mark the basis of the pie shape cut. Mark half in front of the square line, half aft of it. This makes angle equal and gives the smoothest transition between frame and subframe. So in your case mark 1/8 in front and 1/8 aft of the square line.
From these marks, draw a line to the 3/32 pilot hole. These lines are your cut marks.
A Sawzall does a great job on this. Cut a total of 4 lines trying to stay within the marked lines.
Bend the rear frame down until everything looks like you want to.
DISCONNECT THE BATTERY, to keep your electronics happy !
Clean the weld area thouroughly. Remove paint down to bare metal to avoid contamination of the weld.
Use whatever weld method you are happy with.
After cool down and clean up touch up the paint.
DONE :co-ol: