My girlfriend enjoys anal penetration, but so far she only experienced it with fingers and a double-ended dildo. We want to try the real thing, but the dildo is rather small, and even on the larger end it's almost half the width of my dick (which has a circumference of 18cm at its largest point, and is also 18cm long). Plus, she's kinda petite and tight, which doesn't help (great in normal penetration though ). The most important thing here is that I don't want to hurt her. We'll apply generous amounts of lube and be very gentle, but I wanted to ask if any of you had any advice about doing it right.