I'll give you a little hint about caster. Cars at one time had negative caster. Some even had a different settings for the left and right.
That's the reason I asked the question. I used to do alignments back in the day.
I have the SPL arms too. My settings now are -2 camber and +6 caster. I still have room to go to +8 caster and - 4 camber if I want to.