Originally Posted by
Rodney
I think I'm most likely wrong about the part about which way the bobbin faces but still, these days it's far easier to find a twin needle/zigzag capable machine than it is to modify a straight stitch to accept a twin needle.
Rodney
That would be my suggestion - get a $25 older zigzag machine (from the 50-60's) and have that available as needed. Make sure to get a center homing machine (needle is in center of hole when straight stitching).
While I love the 15-91, it's not a suitable machine if you want to sew much with stretch fabric. It was a big deal at the time (50-70's) to get a machine that would sew the "new" stretch fabrics. Remember double knits and leisure suits?