hi i have the same set up as you. first i use the superior
thread count 50. the tension thing the little notch on the
button i have straight up and down. and i use the same
needle as you HLx5 but i use the 90/14 i only use
the needles i get from the dealer. i get five in a package
from the dealer. maybe you are going too fast do you
have a stitch regulator on it. mine is on 5, the stitch
regulator.