Thanks. Unfortunately I didn't get a chance to make any instruction as I had to rebuild this a couple of times to get to this design. Sorry about that.
But as I'm a freak for details my pics on the site are pretty decently sizes for reference as you or your nephew attempt to build.
I've added an extra shot and updated my article for you that covers the back view of the Mod.
Here's a preview of the extra image.
Hope that helps.
Oh and if you need extra reference on location of Pins to fit modulars I used this reference.http://www.eurobricks.com/forum/index.php?showtopic=36535
it helped alot when I was building it.