Having examined the inside of my Lancair wing thanks to a fence leaping up at it, I can assure you the spar material is "marginal" for this span/weight (25 years flying thermal sailplanes if you want to know...). I repaired it and still fly it regularly - love it - but certainly keep the G's to scale levels.

A metal plate mounted to bridge the 2 main UC mounts is a good idea though - stops landing forces trying to pry the wing join apart. Glassing the centre won't stop the spars snapping, just define the likely snap point! - i.e. right where the glass stops.

Cam