You can really adapt a lot of, what is essentially, the basic design.
I must warn though, that adding fans to the outsides of the tubes, especially the incoming air tube, would cause a direct accelerating effect on the cpu fan. As much as this sounds like a super cool idea (being that you would be approaching a jet engine-type design), it would put excessive stress on the cpu fan and it would burn out VERY fast.
Above and beyond this, one could go as far as to replace the cpu fan with a high endurance fan, but noise from this might be excessive.
Furthering that train of thought would inevitably (especially in amateur designs) cause eddy's (please note that an eddy is strictly only applicable to fluid dynamics, but has recently seen similar effects in air dynamics).
Just for now, an Eddy is a dead spot.
These Eddy's will in the end, not only restrict airflow along the unaffected areas around it, but also allow for heatpools to start building inside these dead spots, and effectively cause massive problems.
Think of it as a small-scale tsunami effect, only with air instead of water.
What I'm saying is: Yes, definitely modify the design as it fits you and your application, but PLEASE DONT PUT TWO FANS BLOWING ALONG THE SAME PIPE, REGARDLESS OF DIRECTION.
EDIT: oh yeah... tools...
I had the good fortune of having the use of some of the tools ad my dad's work. They had an engineering department that allowed me to borrow from time to time some of the lesser tools.
A small figure saw with a metal blade and some guide-constructs can be gotten for cheap-ish at hardware stores. No saying cheap just outright though, but good tools to have in the long run if this is a serious hobby to you.
PS: You can also start selling some of these cases you make at decent prices to some pc shops. Stay away from chains like Incredible Connection etc... they wont even bother to see you.
