Answers to some questions/concerns:
I just went out and raised the prop rod with the hood held open by the struts. The top of the rod falls 2" short of the support hole, so that's the extra height you get.
To reduce the chance for rust, I applied some primer to the drilled body holes and let it dry. You are drilling through 2-3 layers of steel; no concern about lack of strength at the bottom mount.
Mine have been installed for nearly a year. No indication of any durability issues at the top riveted mount either. I see no need to add a 3rd rivet.
Just dropping the hood to close it may not work in Summer or warm climates, depending on how your hood latch has been adjusted. Gas pressure rises with temperature, so the struts don't "release" as high. My hood had to be dropped from nearly 24" to close, so I shimmed the latch bracket. Now I can secure the hood with light downward pressure. I carry a small clean cloth or handkerchief so as not to leave fingerprints in the wax.
Like all other hood/trunk struts, they will lose pressure over time, then won't hold the load in Winter. I usually get about 10 years out of the factory set on Japanese cars. In warm climates, they will last longer. The struts are a standard size, so can be easily replaced when they wear out.
There is an "after installation" pic on my web space:
http://members.cox.net/n0v8or/web_index.htm