Great ideas Kenny.  You should put your sharpening jig out on Thingiverse.  

I've found that it doesn't require very high infill percentages to be strong.  I tested one of those plane handles I printed for you a while back by smacking them with a hammer and they didn't even dent, Of course it was mostly a solid shape. It may be better or at least as important to pick an infill pattern that doesn't give you voids because of thin round or angled sections.  

Maybe I do not understand how a bench block is used.  Is there a reason it would be hollow underneath?  

--Nathan, TX. Hire the lazy man. He may not do as much work but that's because he will find a better way.