7 should do it on almost anyone.
However much they actually notice will be different from girl to girl ... and also vary by the amount of their excitation levels.
To hit bottom and pop on through to the other side (some dig this if they're really warmed up, but most will go "Ow!!!, Get the F*** away from me!") ... 7 to more than 8.3 (?), again depends on the girl. I think some chicks are built so that a direct presentation of the cervix isn't available, so you're going to hit off center and just stretch the whole thing up and away.
While on the subject sortof, here's a nice visual/tactile trick to do:
Where she can see what you're doing, grab your rod with both hands (hand over hand) and only insert whatever is leftover.
That won't be amazing for most of us, but the amazing part is still to come. --
Then remove the hand closest to the end (you'll still be gripping it with the other hand down at the base) and put it back in. Use it for a bit.
This will seem for combined effect (length x width = volume displaced) like a normal dick - more or less.
(You can also use the final hand to shake it around a bit while it's in there. I think I got this from Peter North, everyone loves it)
Then remove the last hand and put the whole thing in there. The difference between 'normal' and the whole thing will be more obvious to her now and you'll probably see her friends staring at your crotch after they've had a girl's night out and chatted about girl stuff. rofl
*
...I absolutely do
