Combining unicode-math fonts: Problems with \underbrace

Question

I switched to XeLaTeX and unicode-math a while ago. I really like the possibility to combine different fonts for mathematical symbols. But now I run into trouble by combining the \underbrace command with content from different fonts. I actually use Asana as my main math font, but don't like its \underbrace, as these are too wide and with too much space between itself and the content. Therfore I wanted to use some from another font, which gave some grapy output:

\documentclass[]{scrartcl}

\usepackage{amsmath}

\usepackage{polyglossia}
\setmainlanguage[]{english}
\setotherlanguage[spelling=new,babelshorthands=true]{german}

\usepackage{unicode-math}
  \setmathfont{Asana-Math.otf}

\begin{document}
  Asana math Blubb
  \[
    \underbrace{1} \quad \underbrace{1+1} \quad \underbrace{1+1+1} \quad \underbrace{1+1+1+1} \quad \underbrace{1+1+1+1+1}
  \]
  \setmathfont[]{xits-math.otf}
  XITS math
  \[
    \underbrace{1} \quad \underbrace{1+1} \quad \underbrace{1+1+1} \quad \underbrace{1+1+1+1} \quad \underbrace{1+1+1+1+1}
  \]
  \setmathfont[]{Cambria Math}
  Cambria Math
  \[
    \underbrace{1} \quad \underbrace{1+1} \quad \underbrace{1+1+1} \quad \underbrace{1+1+1+1} \quad \underbrace{1+1+1+1+1}
  \]
  \setmathfont[]{latinmodern-math.otf}
  Latin modern
  \[
    \underbrace{1} \quad \underbrace{1+1} \quad \underbrace{1+1+1} \quad \underbrace{1+1+1+1} \quad \underbrace{1+1+1+1+1}
  \]
  \setmathfont[]{texgyrepagella-math.otf}
  Neo Euler
  \[
    \underbrace{1} \quad \underbrace{1+1} \quad \underbrace{1+1+1} \quad \underbrace{1+1+1+1} \quad \underbrace{1+1+1+1+1}
  \]
  Asana as math font, change font for underbrace only:
  \setmathfont[]{Asana-Math.otf}
  \[
    \underbrace{1} \quad \underbrace{1+1} \quad \underbrace{1+1+1} \quad \underbrace{1+1+1+1} \quad \underbrace{1+1+1+1+1}
  \]
  \setmathfont[range=\mathunder]{xits-math.otf}
  XITS math
  \[
    \underbrace{1} \quad \underbrace{1+1} \quad \underbrace{1+1+1} \quad \underbrace{1+1+1+1} \quad \underbrace{1+1+1+1+1}
  \]
  \setmathfont[range=\mathunder]{Cambria Math}
  Cambria Math
  \[
    \underbrace{1} \quad \underbrace{1+1} \quad \underbrace{1+1+1} \quad \underbrace{1+1+1+1} \quad \underbrace{1+1+1+1+1}
  \]
  \setmathfont[range=\mathunder]{latinmodern-math.otf}
  Latin modern
  \[
    \underbrace{1} \quad \underbrace{1+1} \quad \underbrace{1+1+1} \quad \underbrace{1+1+1+1} \quad \underbrace{1+1+1+1+1}
  \]
  \setmathfont[range=\mathunder]{texgyrepagella-math.otf}
  Neo Euler
  \[
    \underbrace{1} \quad \underbrace{1+1} \quad \underbrace{1+1+1} \quad \underbrace{1+1+1+1} \quad \underbrace{1+1+1+1+1}
  \]
\end{document}

Is there any workaround for this? Or is it in general no good idea to combine different math fonts?

I'm in general not so sure if to stay with unicode-math, as the compilation speed slows down, and for example the XITS font has much too narrow spacing sometimes (using XeTeX, Version 3.1415926-2.4-0.9998, MiKTeX 2.9)

Annotation

According to the first comment I just tried the TeX Gyre Pagella Math which also seems to be a nice font with better underbraces than Asana-math. But this brought me just to another behavior of unicode-math with XeLaTeX I have noticed before already but forgotten about. If I run the following code:

\documentclass{article}

\usepackage{amsmath}
\usepackage{unicode-math}
\setmathfont{texgyrepagella-math.otf}


\begin{document}
Test.
\begin{align*}
  \frac{1}{x^2} \quad \underbrace{1+1+1+1+1}_F \underbrace{1+1}_F \underbrace{i}_F
\end{align*}
\end{document}

Some minor changes that do not directly affect the math environment can change this behavior:

\documentclass{article}

\usepackage{amsmath}
\usepackage{unicode-math}
\setmathfont{texgyrepagella-math.otf}


\begin{document}
\begin{align*}
  \frac{1}{x^2} \quad \underbrace{1+1+1+1+1}_F \underbrace{1+1}_F \underbrace{i}_F
\end{align*}
Some text.
\end{document}

I once got a similar behavior when I did a beamer presentation (using Asana-math, if I remember correctly) where changes anywhere in the TeX code could affect the braces in the shown way. I thought that this would maybe depend on the special circumstances of using beamer, but apparently hopping underbraces can appear anytime. Did anybody else see such a behavior of the \underbrace command before?