Leaving the vectors, levers, analysis and math aside, let me give a minor real world example.  I replaced our Westy's failing struts with two of the "strong" struts from Bus Depot.  Very happy with the hatch not hitting me on the head after that.  We use a hatch-mounted strap-on composite Saris Bones rack to carry bikes with us.  Don't know the weight but it's probably lighter than any one bike we'd put on it and probably way less than a Gary Lee rack or ladder. The hatch will stay open with the Bones rack in place.  With any one bike on that rack the hatch will NOT stay open and we must use an additional prop to hold it up, assuming we can open the hatch high enough to get the prop in place.
If anyone wants, I will weigh both the Bones rack and a bike that has been on it in order to provide actual numbers for the math mentioned above. Photo of the Bones rack on my van in this thread, fourth post down.
TheSamba.com :: Vanagon - View topic - Anyone using a Rhode Gear bike rack on your rear hatch?
  
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TheSamba.com :: Vanagon - View topic - Anyone using a Rhode Gear bike rack ...
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Stephen 

    On Sunday, June 4, 2017 11:59 PM, OlRivrRat <OlRivrRat@COMCAST.NET> wrote:
 

         Or, as in the Immortal Words of Rooster Cogburn >

" Missy, Out Here Everything Just Depends "

On 4 Jun , 2017, at 8:43 PM, Alistair Bell wrote:

> Roman,
> 
> I should put up or shit up about this. It might be time for the old school method of graph paper, pencil, protractor, ruler.
> 
> But you get my drift don't you? The hatch strut to body connection point is one focus, the strut to hatch connection is another, the hinge , the weight, the changing angles and resulting change in force direction when hatch is closing....
> 
> Blah blah blah :-)
> 
> I wish I had the chops and the software to make an animated diagram showing all this.
> 
> Alistair
> 
> 
>