TikZ: Skinny ellipse around two horizontally and vertically offset nodes in a tree

Question

As a follow up question to draw an ellipse into a Tree picture -tikz package, how would one go about making a skinnier ellipse that encircles two horizontally and vertically offset nodes in a tree?

MWE

\documentclass{article}

\usepackage{tikz}
\usepackage{tikz-qtree}
\usetikzlibrary{shapes,fit}

\begin{document}

\begin{tikzpicture}
    \Tree
    [.\node(1){asdfasdf};
        [.\node(2){hjklhjkl}; ]
        [.qwerqwer ]
    ]
    \node[draw,ellipse,fit=(1.north east)(2.south west)]{};
\end{tikzpicture}

\end{document}

Result

Desired result

(Line thickness and color are irrelevant; excuse the shakiness of my freehand drawing with a mouse.)

Answer 1

First idea: draw the elipse sloped along the path wich joins those nodes:

\begin{tikzpicture}
    \Tree
    [.\node(1){asdfasdf};
        [.\node(2){hjklhjkl}; ]
        [.qwerqwer ]
    ]

    \path (1.south) -- (2.north) 
      node[midway, sloped, draw, ellipse, 
           fit=(1.north east)(2.south west), inner sep=2pt]{};
\end{tikzpicture}

Result:

Second idea: for finer control, \usetikzlibrary{calc} and the let..in syntax to compute the required size of the ellipse:

\begin{tikzpicture}
    \Tree
    [.\node(1){asdfasdf};
        [.\node(2){hjklhjkl}; ]
        [.qwerqwer ]
    ]

    \path let
         \p1 = ($(1.north east)-(2.south west)$),
         \n1 = {veclen(\p1)}
         in
         (1.south) -- (2.north) 
         node[midway, sloped, draw, ellipse, 
              minimum width=\n1, minimum height=\n1/2] {};
\end{tikzpicture}

Result: