Just an added note.... If you use #11 Style caps and you get the right nipple you will not really need to add additional water proofing.
If you look closely at your #11 caps you should se the side of the cap are convoluted. If you purchase a nipple with the nipple stack built to right diameter - then with a solid capper firmly push the cap down tight on the nipple stack. the firm placement will stretch the the convolutions flat against the stack.
If you look closely at this pic you can see the convoluted sides of the cap

A couple of the nipples that has a nipple stack with the right dimensions is:



This picture shows the testing of the cap fit to the nipple post


This is the Traditions brass capper I use to place the cap on the post.

Now, here is the catch... If you go with this information push/place a nipple on one of these posts the only way to remove it is shoot it off or peel it of with the edge of a knife blade... They are that tight!