Hi Frank, you have it right in your drawings. The one with the "X" is exactly correct and the way I will do the mount for the cylinder. Here are a couple of pictures to illustrate what I will do. Here's the hatch in the open position, with the cylinder fully extended.
Here's a closer detail of how it will look, just a WAG at the exact location, because the side panel with the actual layout is on the bottom for now.
With the hatch in the closed position, this is the relationship of the points.
I'm not sure I follow your thinking about a sideways load (lateral forces?) on the strut itself. With the strut in place and firmly attached at the pivot points, I don't think there can be any side loading, as long as I locate the axis of the strut in a single plane. Even if I "miss" by 1/4" or so, the side loads shouldn't come into play. Also, I'm using my "X" instead of the "tick" because of the loading on the struts. With the "tick" design, there is a huge increase in the loading of the struts and the corresponding weight they must carry. The closer to the hinge the attachment point is located for a strut, the greater the force necessary to hold the hatch in the open position. The least amount of load would be at the bottom of the hatch, but this isn't practical due to the open length necessary for the strut and amount of travel it would take.
For example (and this is just the theory, not hard science, which is beyond my abilities) let's look at a sample hatch. The hatch weighs 100#. Measured at the open position and with the support on a scale directly beneath to "load" (the back (lower) edge in the middle of the open hatch's edge) the scale reads 50#, about half the actual weight, because the hinge is holding 50# and the scale is holding 50# (on the opposite end). About half way between the hinge & the opened edge, the load would be twice what the weight is on the scale, due to the increase from leverage, or about 100# (this would be my example and your "X" diagram). If that point on the hatch is moved 1/2 the distance closer to the hinge, the load doubles again, let's say to 200#. This is why I'm locating things where I am. If it doesn't work, I'll let you know, but it will be a while until I get to that point in the build. Still too many things to do for now.
If there are any engineers out there who can explain my mistaken theory in simple terms, I would appreciate it. If I'm making a mistake here in logic, planning or execution, please let me know now..... tim