That's cuz ur spex don't equal 15lbs, they equal 13.5 and 19.5. :nana:
I also tried .070, .072, and .074. Wasn't happy with any of them, including when I'd drop the .080" down to F or E. The best compromise was to go too light, and play with a really light attack, but the ultimate solution for me was to sell the guitar.
19-85 is way too small for a bass VI. I use 26-95s on mine in E standard.