Ok here we go
@bumpo83 haha... This discussion gets interesting because of the verbiage used by both the manufacturer and consumers. The following has been muddied by myths, old/irrelevant information, plain old incompetence, etc..
Here is the purpose of sub frame spacers. Unlike older Subaru’s our rear sub frame incorporates 100% of the suspension components. That includes the short trailing arms so when you lift the car the rear wheels get pulled forward. Sub frame spacers simply ‘correct’ that. In older Subaru’s you could space the trailing arm mount alone to achieve the same thing which in my eyes is much better. Functionally sub frame spacer completely rob the clearance you would have gained. Aesthetically the car appears 2” taller. Some will also claim that they save wear/tear on the rear CV’s but they’re completely fine due to the length of the axles and the resulting angle. The fronts are under significantly more stress. So the bottom line is do you need sub frame spacers? Absolutely not. If you want to run 245/65 17’s it’s going to be tight out back without them and I’m sure it’s one of the reasons Ready Lift only did 1.5” lift in the back.
Also I think that when they claim their lift retains factory caster/camber they were only referring to the front and the fact that there is no need for additional cam bolts or adjustable arms front or back. This isn't surprising since things don’t really start changing until you go above 2”.
Here are a couple more POI’s that Ready Lift and many others confuse...
Lifting doesn’t help fit larger tires on this car. The largest tires that fit at stock height are still the largest tires that fit at 1”, 2”, or 3.25” where my front sits.
Sway bar endlinks for our car would need to be SHORTER in the front and longer in the back to correct the angle of forces acting on them after a lift. It’s 1:1 (lift:length) up front and 1:0.5 in the back.