Since I keep getting PMs about this mod, and I needed to get a couple more MM of clearance in the rear. I decided to purchase a new set up rear springmounts and recut them, taking a little bit less off this time. Credit goes to Gsedan35, who was the first to do this, and Borahatch for giving me tips on how to go about cutting the mounts.
See Gsedan35's DIY on installing springs to remove the rear springmounts.
The pieces look something like this:
WD-40 or similar lubricating spray
Start by taping a ring around the springmount of exactly how much you want to cut off. How much you cut will be how much more drop you will get so measure accordingly before cutting. I used Duct tape, but anything will work as long as it sticks to the rubber. I don't recommend blue painter's tape, because I used it the first time and it doesn't really stick to the rubber.
Next, get a rag or in my case some disposable gloves and insert into the hollowed out end of the springmount to provide a cushioned area for the C-clamp to seat to. Install the C-Clamp like in the picture and tighten until the springmount is difficult to rotate/move. Make sure to not overclamp or you can crack the plastic.
Insert the C-Clamp into your vise to provide a stable cutting rig
Get out your hacksaw and WD-40 or equiv
Begin by lubricating your hacksaw blade and springmount by spraying WD-40 onto the blade and rubber, and begin sawing along your tapeline. The outer ring of the springmount is rubber, but the inner ring is made of a plastic, so saw through the plastic. Loosen the clamp and rotate the mount 1 notch and retighten and continue sawing until you cut all the way around the mount, being careful to cut as straight and evenly as you can.
Once you finish cutting, you should end up with something that looks like this, they aren't exactly straight, but close enough, I've been running them for 6 months and no problems here
Here is a comparison of the height difference after cutting, ~1/2"
Reinstall in stock location
End up with a even drop! Dropped on 350z Tein H-Techs, but will work with any spring
Be prepared for camber issues in the rear, just like any drop in the rear over 0.4", I installed the SPC rear camber kit as well and will be getting an alignment soon.