Dont give up so fast, at least do the measurments acurately and see what you have to work with.
Play with the CG afterwards. The plane will be so much more enjoyable after you made any possible mods.
I would asume the GP Stearman could be a a turnkey biplane as they have better QC and the BH may need builders input to ensure correct fit.
Of course there are ways to correct incidences.

Start with the body, engine and the stab, then the top wing.
Others will chime in eventually.