Last year over the summer, I completed a Stance air cup upgrade (cups only). I don't know why I never updated my thread with the progress, probably busy helping other owners with their kits on the facebook group pages... Anyways... here it is...
The solution to this is simple. As you are lowering the perch and as it is approaching the control arm, grab another jack and lift the lower control arm from the lower ball joint area, slowly, as to create more clearance for the perch to be swiveled down more. Once you reach desired height, be aware the at full droop your perch collar WILL come in contact with the control arm. It will not damage anything significantly to affect safety or performance.
This is literally EXACTLY what I did. My first cup kit set up, back in 2014, utilized 65mm ID, 8kg, 5.5in swift springs on the front of my KWv3. Because the KW spring ID is 61mm, there needed to be a spring reducer at the bottom perch to compensate for the bigger ID. I was advised to use a delrin reducer that sat on top of the OE kw helper, replacing the stock yellow kw spring reducer entirely, which worked fine. Over time and after much use, the delrin reducer ended up cracking. Around this time I had gone with 16/17 wheel set up and needed more lift than what I was running at the time. I decided to hop on the bandwagon and buy a pair of Stance cups due to their lift capability (~3.5 inches vs my previous ~2in) I decided to go back to the stock yellow kw spring reducer but I had some delrin/acetal washers made to fit around it. I was told this is beneficial for the health of the pistons inside the cups, as to prevent/reduce coil binding.
After mounting everything in, I was not too comfortable with the way the Swift spring sat over the stock yellow kw spring reducer. This is okay for the struts w/o air cups but I figured it would be better to have the main spring sitting flat at all times as to prevent premature scouring along the inner walls of the air cups (I imagine slightly uneven compressed weight sliding up and down inside the cup was not a good thing). I went ahead and disassembled it again and this time went with the KW club-sport spring 8kg (rate), 140mm (height), 61mm (inner diameter). I also replaced the stock yellow kw helper spring with a 61mm ID one from Hyperco. The design allows the main spring to sit completely flat once fully compressed. Here is a picture of assembly, I do not have a picture on hand whilst fully compressed.
I know this doesn't relate entirely to OP or the question asked by @
JJM4life but figured I'd post this here in case it can help someone.