If you use even the 2 layers of plastic looking stabilizer, it is perforated and the design pulls away. So in my experience I always use a WS material type of stabilizer.... The plastic type of WS if for toppings.. ie to use with towels, fleece etc. Here is a link to what I'm talking about.

http://www.annabovecollections.com/embroidery_store/Water-Soluble-Backing-FABRIC-24-x-10yds-P67C34_product1.aspx

There's a heavy gauge plastic type ws, called badgemaster, that you can use. But the thin one won't do. So to be safe use the clothlike type, like the others said.

Thank you for the informations. I took note too when I'll feel confident enough to do FSL.
Apparently it is very addictive !!??

The only way I have sucess is to use 2 sheets of h20gone and 1 sheet of organza, almost never messes up.

I have just started doing FSL myself but so far have not had much problems, one goofed up because the WS moved so learned to make sure it is tight in the hoop, other than that my machine was acting a little goofy thread tension but now stitching so nice been going like crazy, actually bought a few rolls of the fiborous WS just for FSL I only use the plastic for a topper.

Thank you for asking this question

If you're using Solvy brand, you need Ultra Solvy to do it right with one layer. Super Solvy just isn't strong enough.

I only ever use two layers of fabric type WSS, I didn't like that plastic stuff so I gave it away!!! LOL!
HNR, Meganne

I only use the fabric type of WSS. I do use 2 pieces as most FSL are many stitches. H&*

I have made many FSL ornaments this year. I use two pieces of fiber looking wash away stabilizer and a piece of fine net I pit the net in the middle of the stabilizer. After washing away and allowing to dry trim the net away like you would on an applique. Works well for me.