Topstitch needle ?
 

I keep hearing that if you use a top stitch needle for free motion quilting you won't get a lot of eyelashes on the back. What size top stitch needle is best for FM quilting?

The LQS recommends a 90/14 Topstitch needle.

I have taken too many free motion quilting classes to know that thread type and size, tension, pressure, needle size and type, and bobbin thread type, all have to play together. It's not just one single thing. 90/14 is for 40 wt thread as it is a large size needle.

.............. ditto .... and add on ....... how fast/slow you are moving the sandwich under the needle.

I seems to me that the coats and clark site had a print out you could use for the thread and needle size to use together. I have a business card sized one I bought at hancock fabrics years ago I use for a cheat sheet. I often use the denim needle for heavier weight fabric quilts. It helps to stop the shredding.

Here is a chart I found with a google search
http://www.sewing.org/files/guidelin...dle_charts.pdf

.... also .... the sandwich itself ....
the type of fabrics, batting, number of seams in front/back, sizes of pieces in the blocks, etc.

I've found how you move the sandwich, bot the speed and the direction, has more to do with getting eyelashes than the size of the needle.

I'm still new at fmq and I had trouble a few times with the thread nests underneath. It was the bobbin thread being in wrong each time. I use the same thread in top and bobbin and a titanium topstitch needle. Lots of practice later and it is finally looking better,

I know that many will say depending on brand of the needle even the 14/90 topstitch can vary.

Agree, and also eyelashes come from moving around a curve too fast. I usually use a 90/14 topstitch, sometimes go down. All depends. My machine doesn't have tension issues, luckily.