Hey...
Crap... I wrote a long letter explaining then it got whiped out....
Grrrrrrrrrrrrrrrrrrrrr
Anyways... Lets try again...

First, it's easiest to set your Nexus in WED under "File" "Map Properties"
Second, you can also set it in a "Winddow Definition File" but you need the Pro Version for that...

To get the Nexus set right, here's what you do...
Fire up the game, then press the F11 key once to see the "Statistics Panel".
Look for the nx line that tells you the game required Nexus...
Then reset your Nexus to slightly above the required amount.

As you continue working on the project and keep adding entities your game will require more memory and trerefore the required Nexus will rise... Just do the F11 thing again to see the change and then reset...

There are a lot of things to be done to get your Nexus as low as possable...
You will want to "Optimize" everything... Like, make sure your textures are as small as possable, use Bones animation instead of Verticie animation, Make your textures .tga only when an alpha is required and use .dds files for almost everything else... Doing all that will lower your file download size and time as well as your Nexus requirement...

After you press the F11 key you will need to press it again twice to get back to the game proper... The second press shows you the game polygons etc...

Look at the manual more...
You will find good info under "Winstart" but you need Pro for this but it is the best way because you get a Starter Window and you can compress all your files into a nice tidy package... Then you can create a self extracting .exe file using other free software...

There is a lot to be learned...
One day I'll build a tutorial...