If you haven't notice the calf pad can be turned up side down.
If you find that it rubs the back of your leg then you could always try turning it the other way up.
Just loosen the front two bolts ( note where the washer goes ) and the pad just slots in .
Now saying that there is one other option which remove the pad all together !?
There's nothing moving behind it so I think there's no problem ( so I've been told ) ?
I can't see adding extra pading would be helpful as it would bend your leg the wrong way !?
I have big calfs and the pad cuts into my legs so need the room