Several good hints above. My 2c compendium follows.
Needle: #60 is quite big enough. Larger will give you problems. (Commercial users go for a larger needle for speed and power, and don’t care about the hole size. We do.)
Thread: very fine – 120 gauge on my scale. Thick thread will give you problems. Stock Gutermann is a shade thick imho, but may work. Fine poly-cotton thread is plenty strong enough.
Stitch tension: this will need tuning for UL fabrics. Practice first on scrap to get the top tension right. Read the manuals about this.
Stitch length: not long: that causes too much puckering. 10 – 12 stitches/inch should be OK.
Presser foot: use a roller foot, not a hemming foot. The later works fine on heavier fabrics, but is very tricky on UL fabrics and slippery fabrics like silk and silnylon.
Pinning: strongly advised for the first few inches. Most UL fabrics are tricky enough to control! I pin full-length just to be sure. Yeah, slower, but it WORKS.
Technique: there are several ways to do this.
* Start with a little fabric showing behind the presser foot and go in reverse to the edge, then forwards. This locks the end of the thread, but can still cause significant problems.
* Start at the edge, go forwards, backwards and then forwards to lock the thread end, but apply tension to the fabric from the front and the back. At the front you just hold the fabric – simple. At the back you need 3 – 4 ” tails on the thread, and you hold these (top and bottom) tightly to apply tension.
In reality, provided you apply tension via the ends of the threads and the fabric at the front, you will get satisfactory results most of the time. Conversely, if you don’t apply tension, I can’t imagine any good results. I have to admit I don’t remember seeing this tip in any sewing books, but I may have forgotten.
Cheers