I use a Quintrex 3.70 dart, with a 15hp Mariner,  that we take to Warroora, Ningaloo etc....goes up on my 100 series no worries. It weighs 75kg so its on the larger side but is an excellent sea boat and I regularly get outside the reef. I bought mine new from All Boats for $4K for hull and motor.

I would go the biggest and deepest you can handle/lift  if you are heading out into the ocean. Makes all the difference when its a bit choppy....A lot of the "rooftoppers" are more creek and estuary boats with shallow gunnels.

Hi Tim.

Car toppers are great, I had one for 4 years. Just remember, if you are going to load/unload it every time you use it, the weight is an important issue.

Not only the hull, but also the outboard. !5hp 2 strokes are fine, they tend to weigh 35 or so kilos, but if you go up much more you'll be looking at 50+ kilos.

The other thing is the beam of the dinghy. I don't know how wide your Patrol is, but it will pay to measure the width of the roof, and the wheelbase and stick to something halfway in between those widths.If you go much over 1.6 meters width it will probably be sticking out a lot? I had a Quintrex 3.75, and the only other 12 foot dinghy that came in below 1.6 meter was a Savage Snipe.  Many newer 12 footers are a lot wider than that. Both of these dinghies are about 85 kilos. The wider ones are also heavier. My Quintrex Dart took me a lot of places, also comfortably 3/4 kays offshore on the right days, and up north that put me into some serious fishing territory! Anyway, good luck and tight lines!