Utemad replied:

I have looked at this on a dual cab but also discovered some interesting info.

You can put an extra cab tray on a single cab but you get a gap between the cab and the tray. People have talked of putting jerry can holders and tool boxes etc in this space. However it would probably look like crap.

As single cabs were available as cab chassis models (unlike dual cabs) there are stuff all ute tubs geting around second hand. I have heard of single cab trays going for about $1000 second hand. Whereas you can get a dual cab tray for $50.

I'd be sticking with the tray you have unless you really really want a style side.