Satoshi, regarding this mod...
You can get the hatch struts to support your new wing. The hatch struts that come with the mechanical wing should be strong enough to support the weight, instead of using the bar.
My hatch would not stay open after the mechanichal wing was installed, it was too heavy. Then they upgraded the hatch struts. These are much stronger than the factory original units.
The part numbers on my struts are as follows:
LH strut - 68630-X3501
RH strut - 68530-X3501
Both are manufactured by Tokico for toyota, and should be available from a Toyota dealership.