Frank, be careful using a single nail knot on intermediate flylines. A nail knot tends to cut through the intermediate outer shell and then slips off the monofilament core. Two nail knots seem to work. Floating and sinktip lines don't appear to be an issue with nail knots.
A whipped loop is a better approach, and even better, is a braided double catch loop.
Newer flylines now come with an integral loop on both ends. Rio in particular, has been doing this for a couple of years.
As a side note, try a three-turn sheet knot for attaching you leader to a loop in your flyline. It transfer energy efficiently without the non-linear loop-to-loop approach.