FVWM: Fvwm3 Virtual Desktop Problem

I have been using fvwm-2.6.9 as my window manager on Gentoo Linux.
My favorite feature is the virtual desktops of which I use a 2x2
configuration.

After discovering the release of fvwm3, I downloaded, configured,
compiled, and installed fvwm3 the same way as I do for fvwm-2.6.9.

When I started fvwm3 using the same config file as with fvwm-2.6.9
there were no apparent problems.  However, my virtual desktops were
missing.  The config file specifies a 2x2 arrangement but with
fvwm3 I only get a 2x1 arrangement.  The lower two virtual desktops
are not present.

Checking the documentation for fvwm3 there does not seem to be
a change in how the virtual desktops should be defined.

Is this a known problem with fvwm3?

Is there anything I can do to get a 2x2 arrangement of virtual
desktops?

LP