slender \lgroup and \rgroup

Question

The default \lgroup symbol in the most of math-mode fonts is thicker as compared to the text- and math-mode alphabets and numbers. A few fonts provide slender \lgroup symbols like newtxmath, mathabx, MnSymbol (and may be others that I don't know). However, when I use any of this with XeLaTeX and fonts like STIX Two Text or Sitka Banner, I get "Too many font symbols declared". I just want to use \lgroup and \rgroup symbols from fonts that provide slender versions along with either STIX Two Text or Sitka Banner. The specific issue here is the location of chemmacros package. If you put this package before mathspec or \setallmainfonts, the code does not work. Kindly respond.

\documentclass[a4paper, 10pt]{extbook}
\usepackage[margin=0.8in, bindingoffset = 0.4in, headsep = 5pt]{geometry}
\usepackage[version=4]{mhchem}
\usepackage[cmbraces, cmintegrals]{newtxmath}
\usepackage{chemmacros}
\usepackage{mathspec}
\setallmainfonts[Scale=1.0, Numbers = {Lining, Proportional}]{Sitka Banner}


\begin{document}
\chapter{\LaTeXe}
\begin{align*}
\angle ABC &= \alpha \\
\dfrac{\cos\alpha}{\sin\beta} + \dfrac{\cos\beta}{\sin\alpha} &= 1  \\
\left\lgroup\dfrac{\dfrac{\cos^2\alpha}{\cos^2 \beta}}{\sin^2\beta} + \dfrac{\cos^2\beta}{\sin^2\alpha}\right\rgroup &= k \\
\left(\dfrac{\dfrac{\cos^2\alpha}{\cos^2 \beta}}{\sin^2\beta} + \dfrac{\cos^2\beta}{\sin^2\alpha}\right)&= k
\end{align*}
\begin{align*}
I &=\int\limits_{0}^{\frac{\pi}{2}} \dfrac{\cos^2 x}{\sin x} + \dfrac{\cos x}{\sin^2 x} \text{d}x \\
J &= \int\limits_{0}^{\frac{\pi}{2}} \left\lgroup\dfrac{\cos^3 x}{\sin x} + \dfrac{\cos x}{\sin^3 x} \right\rgroup\text{d}x 
\end{align*}
\end{document}