I don't ride tires that wide or at that low pressure, so treat this as speculation.
The best success I've had with glueless patches has been with tubes close to the tire size (no 22-35 tubes in a 32 tire, please!) and fairly high pressure (70-90 psi). I always figured the high pressure, along with proper tube sanding, was responsible for holding the patch in place until the sticky adhesive set. If somebody knows better, or has a good reason for speculating to the contrary, I'd be interested to hear it!