Dear Tor,
Oh, really good to know, I think I have been using too small needles in general, also for the canvas.
I've been using the TKT 20 the whole time because I like the look of the thick thread.
I was just about to order some needles right now.
The guy at the industrial machine place suggested 110 needles and TKT 30 thread when I said I was busy with canvas.
But I forgot to mention that I wax the canvas, which also makes it quite thick and I have indeed been having a hard time finishing the seams of the bags with twill tape (because there are some spots with 5 or 6 layers of canvas).
Enclosed are some photos of bags that I made with the 110 needles:
Best,
Audrey