BE VERY CAREFUL!
I wanted to improve upon the already existing struts for three large and heavy hatches on my boat. I am quite good at various things DIY. I also understand geometry and physics to a certain extent...and both come into play here.
After a little research, I determined that these rather expensive gas struts come in a large variety of lengths and pressures. In order to increase the chances of getting it right the first time, thereby reducing return & exchange costs, I opted to have my boat yard deal with this project. They're very good at all kinds of "special" projects and very clever, but this one gave them headaches to the point where I decided to cancel the project altogether. I say be very careful because with the angles and leverage involved, it could be easily possible to snap a bracket or crack fiberglass or have a strut punch through a hatch or, worse yet, injure somebody.
I will eventually get back to this project somehow, someday. I'm not trying to suggest you shouldn't untertake it. I'm just warning you that it can be more complex and even dangerous than it might appear to be at first glance.