PDF output wrong size

[Les]

On Tue, 3 Mar 2020 11:10:42 -0700
Richard Opheim <r.a.opheim at gmail.com> wrote:

> Sorry about that. It's been a while since I posted.
> I'm running LyX 2.3.4.3 on WIN10. The class is memoir. I specify that
> the paper format should be 8 x 5, but the program doggedly outputs to
> 8.5 x 11.

The memoir class ignores LyX page sizes. You have to define them in
the  preamble.

Here is what I have put in the preamble to solve a similar problem:

\setstocksize{9in}{6in}
\settrimmedsize{9in}{6in}{*}
\settrims{0pt}{0pt}
\settypeblocksize{7.7in}{4.5in}{*}
\setulmarginsandblock{24mm}{20mm}{*}
\setheaderspaces{0.625in}{*}{*}
\setlrmargins{0.75in}{*}{*}
\setlength{\marginparwidth}{0.0in}
\setlength{\uppermargin}{0.7in} %Top margin including header

-- 
Les Denham