Maurie replied:

Peter I waited to see if you got any answers as I am interested as well. I have a 3.5m dinghy that I want to carry on a Hilux dual cab. I am going to support the dinghy at the 1.5m points as I believe that the gunwale extrusion is quite strong and should support the dinghy but time will tell. I saw a rodeo with a dinghy secured from the tray to the cab effectively making the cab and tray one unit but he was only travelling on sealed roads so he didn't have any problems but off road would be a different matter. I have just seen a setup with a rack built right across the back and half of the roof supported on the back but this setup was horrendously heavy but on the upside the setup has been to cape york and back with no problems.
Let me know if you have any better ideas.

Member - Mal replied:

Peter, There are two ways of doing it, both having support solely from the ute back. 1. Let the tinny hang out over the rear by 750mm and have 1250mm of the bow going foward suspended clear of the cab roof. 2. Have a system made up which has a canterleaver over the cab. The rack or frame has uprights in the four corners of the ute back with horizontal bars across at front and rear, and bars running lengthways from front to rear. In the second method the lengthways bars extend over and clear of the cab and are joined at the front by a horizontal crossways bar. Aluminium scaffolding tube would work well. Lots of luck, Mal Try.