All planes are flying collections of compromises...
When rubber hits the road (or in this case, when wood hits the cut-table) some compromises have to be made. No way round it.
For example, 1.5mm plywood comes in 2500 x 1220 sheets. The front wing has a 1200mm chord. That places (ideally) the front spar at 25% chord (or 300mm from the leading edge. So far, so good. But that makes the leading edge piece more than 600mm, leaving too little remaining plywood to cover the top or bottom without significant wastage - and at $120 per sheet, wastage is a sin.
So I have had to reposition the main spar in a sub-optimal position just to stay solvent. Here's what I've ended up with:

As you can see, each section is under 600mm, meaning I get to waste very little plywood, but the main spar is slightly forward of where I'd have liked it to be. Bugger.
Such is life...
Duncan