Wide hat doesn't stretch (much)

[thruston]

The \widehat symbol does not seem to stretch in the way that it does in other fonts, as this example shows:

\documentclass{article}
\usepackage{fontspec}
\setmainfont{TeX Gyre Pagella}
\usepackage{unicode-math}
\begin{document}

\setmathfont{TeX Gyre Pagella Math}
Is the hat as wide as we need: $\widehat{\mathstrut α_1-α_3}$ ?

\setmathfont{Neo Euler}
Is the hat as wide as we need: $\widehat{\mathstrut α_1-α_3}$ ?
\end{document}

Perhaps Neo Euler could borrow some of the symbols from TGPagella?

(I'm not saying that this is a good notation by the way! It's someone else's that I need to follow.)