I just but them together, no over-lapping, and do wide long zigzag. Can't even tell the join is there when quilt is quilted.

Nancy's Notions has it in the early summer catalog @$12.99 for 2 - 10 yard rolls. I've been going to order some but still haven't gotten around to it. I've got a lot of batting pieces & I never have very good luck with zigzagging mine together so if this works I'll be able to use up a lot of my misc. pieces.

This is the stuff. I bought some at the Long Beach Quilt Show. Can't wait to use it. Much better than zig-zagging batting together!

http://heatpressbattingtogether.com/index.html

I make my own strips from lightweight fusible interfacing. Once the quilt is quilted, it will stay in place for sure. I've never had a problem with this method. I am guessing that the product on the roll is convenient because they did the cutting, but I can get interfacing so cheap, especially when JoAnns has it on sale.

Justm trim edges straight, butt the edges together and do the longest, widest zig zag you can. IOt is perfect, and far cheaper than the tape.

Well now, aren't you the smartie?! Why didn't I think of that!

Isn't that the truth..........

I usually just butt up the edges and use a big zig zag and it works just fine. Maybe it's the type of batting you use. You could have the batting pieces together like you were going to sew them, overlap a couple of inches, cut a very gentle curve through the overlap. Remove the overlap. You should have a matching curve edge. Try zig zagging that together. That should help you know where you need to match up as you go along and hopefully avoid stretching. HOpe this is clear.