Increase size of angle brackets with kpfonts

Question

I am using kpfonts and have run into a problem trying to use large angle brackets in math mode formulae. Based on the answers to previous questions e.g. Big Parenthesis in an Equation I have defined additional sizes \vast and \Vast and these work with the standard rounded and square parentheses but they do not work with the angled brackets \langle and \rangle. As far as I can see, neither does \bigg as the following MWE shows:

\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage[partialup]{kpfonts}
\usepackage{graphicx}
\usepackage{siunitx}

\newcommand{\e}{\,\mathup{e}}

\makeatletter
\newcommand{\vast}{\bBigg@{3}}
\newcommand{\Vast}{\bBigg@{4}}
\makeatother

\begin{document}

\begin{align*}
    &( \big( \Big( \bigg( \Bigg( \vast( \Vast(  \\
    &[ \big[ \Big[ \bigg[ \Bigg[ \vast[ \Vast[  \\
    &\langle \big\langle \Big\langle \bigg\langle \Bigg\langle \vast\langle \Vast\langle \\
    &\Vast[\frac{\frac{gk}{\omega} A_0 \e^{{k}{z_n}} \biggl[\cos{\Bigl(\theta + k\bigl(x_n+\tfrac{\delta{x}}{2}\bigr) - \omega t\Bigr)} \biggr]}{\frac{gk}{\omega} A_0 \e^{{k}{z_n}} \biggl[\cos{\Bigl(\theta + k\bigl(x_n+\tfrac{\delta{x}}{2}\bigr) - \omega t\Bigr)} \biggr]} \Vast] \\ 
    &\left[\rule{0cm}{1.3cm}\frac{\frac{gk}{\omega} A_0 \e^{{k}{z_n}} \biggl[\cos{\Bigl(\theta + k\bigl(x_n+\tfrac{\delta{x}}{2}\bigr) - \omega t\Bigr)} \biggr]}{\frac{gk}{\omega} A_0 \e^{{k}{z_n}} \biggl[\cos{\Bigl(\theta + k\bigl(x_n+\tfrac{\delta{x}}{2}\bigr) - \omega t\Bigr)} \biggr]} \right] \\ 
    &\Vast\langle\rule{0cm}{1.3cm}\frac{\frac{gk}{\omega} A_0 \e^{{k}{z_n}} \biggl[\cos{\Bigl(\theta + k\bigl(x_n+\tfrac{\delta{x}}{2}\bigr) - \omega t\Bigr)} \biggr]}{\frac{gk}{\omega} A_0 \e^{{k}{z_n}} \biggl[\cos{\Bigl(\theta + k\bigl(x_n+\tfrac{\delta{x}}{2}\bigr) - \omega t\Bigr)} \biggr]} \Vast\rangle \\
    &\left\langle\rule{0cm}{1.3cm}\frac{\frac{gk}{\omega} A_0 \e^{{k}{z_n}} \biggl[\cos{\Bigl(\theta + k\bigl(x_n+\tfrac{\delta{x}}{2}\bigr) - \omega t\Bigr)} \biggr]}{\frac{gk}{\omega} A_0 \e^{{k}{z_n}} \biggl[\cos{\Bigl(\theta + k\bigl(x_n+\tfrac{\delta{x}}{2}\bigr) - \omega t\Bigr)} \biggr]} \right\rangle \\
\end{align*}

\end{document}

which generates:

NB ignore the content of the formulae, just there to illustrate the point.

What I need is to be able to generate the second sample formula, but with angled rather than square brackets. So I need \langle and \rangle to scale with the larger manual controls or with \rule.

They do scale with the mathpazo font, but I ran into other problems with that font and am reluctant to change font again. But neither can I swap from using \langle and \rangle as it has a specific meaning in my work.

Can anyone suggest a way for me to stretch \langle and \rangle whilst continuing to use kpfonts?

Thanks.