ghostrider

If you're set on a Pellon product as the Timtex substitute, that would be the Peltex 70, 71, 72 (the only difference is in how many fusible sides it has) that you've already tried. It was most likely the density, not the thickness, that stressed out your machines.

Fast2Fuse is an option no one has mentioned yet. I love it, as does my Bernina. It comes in three weights, all are double sided fusible. The main disadvantage is it's price. I use Fast2Fuse for journal and legal pad covers and Décor Bond for boxes. I don't make bags, so can't give you experiential advice on either brand for that use.

However, here are some comparisons that may help you out.
http://nicolemdesign.blogspot.com/20...nd-pellon.html

http://nicolemdesign.blogspot.com/20...onderings.html

Raggiemom

The machine was okay sewing through the fabric, batting, Timtex to for the quilting. It objected when I had to pinch the corners at the bottom. It's just so thick since there are essentially 2 layers of Timtex at that point. I'm wondering if I could cut the Timtex off at the corners before I pinch them somehow.

citruscountyquilter

I've been reading about a sew in interfacing called Stiff Stuff here on the Board. I haven't tried it yet but from what I've read people really like it for bags and other things. I was going to try it in place mats. If you google it you will find numerous references to it but make sure it is the interfacing as stiff stuff is a name of something used in crafting. From what I gathered it was not thick but rather stiff.

gale

I used 71F (one side fusible peltex) and it was fine in my 6600. On the other hand, I used the double sided fusible recently and my machine handled it but I hated it. That was the 72F peltex.

laughingquilter

are you using a walking foot?....I've used the fusible (one side only) stuff but I don't think my machine would be happy if I tried sewing it without my walking foot.