I think you should check ZNline and or Composite ARF web sites.
http://www.composite-arf.com.hk/ar/Product?701000
Click on Electric power Hacker.
It's JPz' Integral, stock airplane with the hacker engine, most popular engine set up in europe !
Well below 5 kg no stress, don't try to reinvent anything, just do like JPZ !
Rgds
Laurent