So the plot thickens. I have 2 pairs of yellow ITC springs here (untouched originals), both are 8.5mm wire thickness with the same amount of coils as the white sets I have. Interesting to say the least. I also have a set of non progressively wound springs with 8.0 wire thickness, 13 coils. These are supposedly a heavier rating but I really am uncertain. Walters springs are a good price, I'll do some testing with what I have but it looks like I may be giving him a call.
K