It is OK to use a larger rivet as long as you have the edge distance. Obviously, that is not a factor on the skins but it might be on the underlying structure. I am not aware of any restrictions on the use of NAS 1097 AD4-(x) "oops" rivets, and I welcome any references to increase my education. That said, the only reason to use "oops" rivets in this case is to make the finished structure look like it was done with the AD3 size rivets. The real reason to buy a new skin, in my estimation, is that the AD4 rivets are harder than AD3 rivets to set, especially bucking blind inside the stabilizer, and at your level of experience you may be drilling out more than a few rivets with the fun meter going way down to zero. If it was me, I'd verify that the edge distance is adequate and then shoot regular AD4 rivets. If that proves too hard for you at your current level of experience you can always buy new parts. Everyone on this list has done that, some more than once I bet. Your level of experience will greatly benefit from this whole affair. Don't get discouraged...Build On!