Inverting Surfski on Factory Roof Rack Rails?

I am not sure that it's just that I mainly see professionals doing it, because they are usually not paying for their surfskis, or if its "ok", but what has the masses found in regards to just inverting the surfski onto padding on the roof rack rails, like for surfboards, and lashing them down from there to prevent any lateral movement? Are the pressures on the hull that much greater than securing it into cradles, such as Goodboy, KayakPro EZ-vee or Epic cradles?

Most trailers just have cross bars and that is how boats are lashed down. What have people found that have done this? Good, or bad?

The ski will be fine. Ranga tied a carbon elite upside down on my car once and then I had a 3 hour drive home at 110kph. Not a problem. The ski needs to be firm. Movement of the ski causes the problems, so as long as the ski is firmly secured it should be fine.

Yeah, before I got my Goodboy, I mounted my first ski (V8) upside down facing forward on the cross bars that had pool noodles wrapped around them. Worked fine.
However I will say, I love the Goodboy vbars. So easy an secure.

One of the problems with securing your ski by just tying it down to your roof rack rails is that in many modern cars the roof racks are very close together many times less than 1m). You have a 6.5m ski that has to be secured onto those rails so it needs to be tied down fairly tightly. As you travel there is a lot of vibration happening on both ends of the ski which puts a lot of pressure on your seams and can cause the ski to crack, particularly in the centre.
That of course is without allowing for the pressure of cross winds etc which can have a huge effect on your ski when travelling at speeds.
Kayak cradles only allow you to secure the ski with less pressure on the straps but do nothing about the vibration, cross winds and other transportation pressures.
We developed a Ski Transport System that allows you to travel your ski more safely in cross winds with much less pressure required on the tie down straps to hold the ski in place and dampens the vibrations during travel as the ski is supported in equal thirds.
It can be easily fitted to existing roof racks and matches current low profile roof rack systems.
Hope this helps.
For full info see www.fitnesspaddlers.com.au

I carry my Cobra Eliminator upside down on a Thule Rack with canoe gunwhale brackets and it works well. The Cobra is plastic and has a flat top though. I would not want to do it if the places I was strapping to the rack were not flat. I do tie to the front footbrace as well as the straps are only about 30" apart, I would not have to do that with a V-Rack.

I made my own roof rack that is 7' long (2.1 meters) with flat pads at each end 6" (15 cm) wide that I covered with closed cell foam.

As others have said, carrying your ski upside down isn't the problem, it's more related to the span of the mounting points and the contact area. Increasing the span and contact area will reduce the load per square unit (overall stress exerted at any one point on your ski) and will reduce the overall chance of damage during transport

Ideally, try to support your ski 7 or 8 feet between pads with 4-6" wide pads covered in closed cell foam. If you do both of those, your chance of damage is greatly reduced regardless of other factors.

I carry my ski upside down and backwards for thousands of miles each year without any issue, so it seems to be an ok system

Cheers