I went up & slightly out with mine too & it worked out perfect for me. when I raise the car & have full droop then yeah, my wheels go way positive, but at that sweet spot of ride height or lower it works really well...
I think ideally would be to set this up as an adjusment point with a cam washer, but that would take a lot of work & include having to drop the subframe completely to set that up right. on full compression my upper arms also just touch the unibody frame rail, I just bent the lip a bit & I'm good, but of course not as low as you are either...
to go as low as you with this mod would require notching the unibody rail & create a pocket for the arm to sit into on full compression. "C" notching is common on full frame cars when bagged for full drop. another option would be building a custom upper arm that has a bit of a Z shape to it... this wouldn't affect the geometry cause all that matters is the pivot points, the arm can be any shape really & as long as the pivots & bj are in the correct location it would still work the same... the wheels not cambering much as it's dropped is good really, but of course if you need this extra camber for wheel clearance to tuck then at that point it's not so good... if I ever have my rear subframe out I'm going to set it up as an adjustment point with a cam washer like the lowers are...