Being that wood over 36" is hard to find and expensive as well almost all kit makers require splicing of wood pieces over 36". It's my own personal preference but I'd never do the splicing in the center of both spars. I splice them at the ends but on different sides. Most wing failures happen in the middle so I want solid pieces of wood across it. Here is an example:

/ = splice
|| = center of wing

Top spar:

-----------------------||----------/-------------

Bottom spar:

-----------/-----------||-----------------------