PlanetsCentral

Does your host.log indicate that PHost is reading shiplist.txt? I just checked host.log from North Star 18, there it says "Using custom hull functions defined in 'shiplist.txt'". PlanetsCentral's games do not generate any such warnings.

Yes:

Portable Host version 4.1h for PC Win32/Windows NT
Copyright (c) 1995-2014 Portable Host Project
Invoked with the following parameters:
    L:\James\VGAP\phost\phost.exe
    ./game01
It looks like this game has just been mastered. PHost is
now creating the data files necessary to run the first turn.
Using custom hull functions defined in 'shiplist.txt'
Writing xtrfcode.txt file...
Random seed is 57712
Game name is 'Game01'
This is Turn #1.
Checking host data...

Could it be that SpaceLord does not like ships with more than 10 weapons?

Not impossible. spacelrd.txt does say "What SpaceLord can't do: - PHost is NOT supported (yet !)" It's quite possible there's an expectation of max 10 beams/bays/torps.

I don't suppose there's any source code for any of these computer players floating around.