settypeblocksize does not change the textwidth

Question

I'm new on using the memoir documentclass and I've been trying to implement a page layout with a large side margin, so I can have margin notes and margin figures, but I've been trying to create an environment that, for specific pages, I get rid of this margin. The code is as following:

\LoadClass[twoside, 11pt]{memoir}

\setstocksize{11in}{8.5in}
\settrims{0pt}{0pt}
\settypeblocksize{7.5in}{4.3in}{*}
\setlrmargins{1.5cm}{*}{*}
\setmarginnotes{20pt}{6.2cm}{0pt}

\checkandfixthelayout[nearest]


\newenvironment{fullwidth}{%
    \settrims{0pt}{0pt}
    \settypeblocksize{7.5in}{6in}{*}
    \setlrmargins{3.2cm}{*}{*}
    \setmarginnotes{0.01pt}{0.01pt}{0pt}

    \checkandfixthelayout[nearest]
}{%
    \settrims{0pt}{0pt}
    \settypeblocksize{7.5in}{4.3in}{*}
    \setlrmargins{1.5cm}{*}{*}
    \setmarginnotes{20pt}{6.2cm}{0pt}

  \checkandfixthelayout
}

It seems to work well, since the layout —visualized using \usepackage[showframe,pass]{geometry}— gets changed propertly, but the textwidth does not. How can I solve this issue?

Answer 1

As @daleif says you can't change the layout mid page, but perhaps memoir's adjustwidth environment is what you can use.

% textwidthprob.tex  SE 643343

\documentclass[letterpaper]{memoir}

\usepackage{lipsum}

\begin{document}
\lipsum[1]

%%% reduce local margins by 1cm and 2cm
%%% (increases local textwidth by 3cm)
\begin{adjustwidth}{-1cm}{-2cm}
  \lipsum[2]

  \lipsum[3]
\end{adjustwidth}

\lipsum[4]

\end{document}

The adjustwidth environment can cross page boundaries.