I have started using the pro knot which is similar to Parnell except the 2nd loop does not go under the anchor string. Instead it just goes back thru the loop of 1st knot. I like it because it is smaller and you don't have to go back under the stringbed a 2nd time. It also seems to pull the string tight up against the frame. If you have a big stretched out grommet at the tie location, a Parnell might be better as it is a wee bit thicker.
But, I exclusively used the Parnell for 6 years as finishing and starting knot without any problems.