Fix Trim size 6.125in x 9.25 in using memoir

Question

I've tried with:

\documentclass[10pt,smallroyalvopaper,oldfontcommands]{memoir} 

\usepackage{lipsum}

\begin{document}

\lipsum[1-9]

\end{document}

I got the PDF output with Trim size as 6.175 inches x 9.25 inches because of the option smallroyalvopaper used, but I need the Trim should be as 6.125in x 9.25 inches with the same text width and height of the option smallroyalvopaper also the page should be both side equal, i.e., text width should be center to the Trim size on both odd and even pages…

Please advise…

Answer 1

Peter Wilson answer working fine, with a small addition, and the modified MWE is:

    % memtrimprob.tex SE 642484

\documentclass[10pt,smallroyalvopaper,oldfontcommands]{memoir} 

\stockheight=9.25in
\stockwidth=6.125in
\settrimmedsize{\stockheight}{\stockwidth}{*} % set the trimmed size
\setlrmargins{*}{*}{*} % equal left/right margins
\checkandfixthelayout

\usepackage{lipsum}

\begin{document}

\lipsum[1-9]

\end{document}