So I've come to a firm conclusion, which I had hypothesized last night. I will most definitely need help with this.

I haven't done any trig since high school, and definitely never any physics or statics.

The spec sheet I linked to is just something I found on the net, not the springs I was specifically looking at. The springs I was thinking about were this brand:

http://www.amazon.com/Attwood-SL34205-Sp...6462&sr=1-1

They're available in a few configurations of force and length. I do plan to use two of them, on on each end of the lid, so we can cut the calculations in half.

That link to McMaster-Carr is excellent, both in terms of calculations as well as component selection. For some reason I had a really hard time finding retail availability of an assortment of gas springs using Google. I probably should have hit that site directly and used their search.

There are a number of considerations with the mounting orientation of the spring that I'll cover in my next post. I need to run a few errands, including taking my daughter for a walk this AM, so I'm out of time at the moment.

Thanks for the very detailed explanations by the way!