FVWM: FvwmCommand docs

I recently installed Fvwm3 for the first time.

I let it install into /usr/local (the default) where I already had
Fvwm2.

First thing I noticed is that it replaced the FvwmCommand binary.
So, while under Fvwm3 I tried to use FvwmCommand.

I get the message:

Cannot find FvwmMFL socket None.
Please start FvwmMFL module from your fvwm configuration.

So, I put this in my .fvwm2rc:

AddToFunc StartFunction I Module FvwmMFL

and took out:

AddToFunc StartFunction I Module FvwmCommandS

restarted fvwm3 and got the same message.

So, then I looked at the FvwmMFL man page, no help.
Then I looked for the FvwmCommand man page, it's missing.

What I would like to see are instructions on how to make FvwmCommand
work and ideally instructions on how to set up my Fvwm config file
to have FvwmCommand work with either fvwm2 or fvwm3.

Also I'd like some guidance on the best way to have a setup that works
with both Fvwm versions.  It looks like I need to put one of the Fvwm
versions somewhere other than /usr/local since there are conflicts.

It looks like FvwmMFL does a lot more than FvwmCommandS does, but
if FvwmMFL was named FvwmCommandS, the transition would be transparent.
I think.

-- 
Dan Espen