tension is a tricky thing to work with. on a long arm, first you make small adjustments to your bobbin case,
with your regular machine, you have to adjust the top tension only, on MY long arm, I have found that I sue the same color top and bottom..no problem..use a different color top or bottom..PROBLEM.., its a fine line we walk.and if we dont get it just right, then the whole thing messes up. I truly understand, and feel your pain, but save yourself a headache, and use same thread top n bottom.
katz