It may be difficult to fully convert him into a Matoran design, since he's not a stereotypical Toa-build style. Do you have an image of his full body? It's hard to visualize it with just close up shots.
Also, it would be useful to have a bio for him. This topic is meant to show the self-MOCs and build up a story with them, so I'll need info on his role in G3.
If you check one of the upper comments by Bokarda, you'll see a link with a general bio template. Just make a new topic with a bio (and a full image), and I'll see what I can do.