I want to use mtpro2 together with Souce Serif Pro, but default mtpro2 looks like too thin.

MWE
\documentclass{article}
\usepackage[lite,subscriptcorrection,slantedGreek,nofontinfo]{mtpro2}
\usepackage{fontspec}
\setmainfont{Source Serif Pro}
\begin{document}
Source Serif Pro $f=|a|/3$ with mtpro2
%Source Serif Pro $f=|a|/3$ with XITS Math
\end{document}
How to make it heavier? Thanke you all in advance
mtpro2specifically, XITS Math matches XITS and comes in a bold weight. – Davislor Oct 03 '18 at 10:27