Now I have a sewing machine with a walking foot (Bernina Activa 145), I'm having another go at my upcycled bike inner tube wallet design (old question from when I tried hand-sewing it); the answer I accepted suggested topstitching but it wasn't tidy enough by hand).
Without the walking foot I couldn't deal with the inherent stretching and I got uneven stitching and puckered rubber. Now I'm using the walking foot that's fine, but the needle doesn't seem to reliably go right through and pick up the bottom thread (I'm not saying the walking foot has changed this; I'm inclined to think it's right on the edge of working and my luck has let me down). Should I be using a thinner needle? A thicker one? Something special? Giving up?