Sarah often asks me to wear an extender/sleeve, one very much like Cokezero's. The one we have has a space in the end bit big enough for a bullet vibrator and we often slip one in which gives extra stimulation to Sarah and myself, would definitely recommend trying this.
Years ago we had a cheapish hollow strapon which my 4.5" cock sat inside and gave Sarah a thick 8" cock feeling, I got very little to no sensation with this which is a strange thing while fucking. The straps eventually frayed and broke and we never replaced it.
However nothing beats a real large cock.