So this past Friday I bought the HD parts to put a detachable passenger backrest and luggage rack on my FXSTSSE2 and did the "grind mod" to avoid relocating the rear turn signals.
It took less than 30 minutes with the following steps;
1. I removed the original hardware (one-by-one) and installed the detach hardware in it's place.
2. Eye balled the side plate where it was going to come in contact with the turn signal and marked the material on the side plate that needed to be removed for clearance with a black sharpie marker.
3. Grind a little, check it, grind a little more, and repeated until I got the first plate to clear the turn signal mount.
4. Repeated the grind process and fit on the second side plate.
5 Assembled the side plate to the sissy bar, added the luggage rack and the backrest pad.
It fit perfectly as an assembled unit!!!!!!!!!!!!!!!
I have pictures to share
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Thanks to everyone that provided me with the insight to complete this installation.