Less is sometimes more. I want to publish really simple hack how to make part of object stronger when you use Skeinforge for slicing. (It’ll probably work even in other slicers). This is part of Skeinforge how-to I’m preparing to publish here.
Why less is sometimes more? When you have void or hole in your object, Skeinforge has to do shells around it. And even will bind some of infill to it. If the hole has perimeter smaller then lets say 0.5mm radius, the overall density in this part of object will increase, the hole wont appear on object anyway and you can save some plastic in compare to increasing overall infill density!!
Picture is more then 1000 words 
Will produce this
More holes you add, more stronger the part of object will be. Of course till you hit state where the holes are too close to each other. Experimentation is needed. In my case, it reinforced the weak parts of X-ENDs in my felt branch of Prusa Mendel.
What I will try next, is small slots in the part, where by rotation of them you could control in which direction object will be stronger. To get an idea, I did a small mockup pic. Again the slots will be small enough to be unprintable, but big enough to force Skeinforge to making stronger infill
