  We investigate the effects of combining next-to-leading order QCD results
with parton-shower effects in $W^+W^-jj$ production via vector-boson fusion
including leptonic decays. Using the Herwig 7 framework interfaced to VBFNLO 3,
we compare the predictions obtained from the angular-ordered and dipole-based
parton shower algorithms combined with subtractive, MC@NLO-type, and
multiplicative, Powheg-type, matching. A consistent treatment of
renormalisation and factorisation scale variations in the hard process and the
parton shower allows to assign more reliable theory uncertainty predictions to
key distributions like the central rapidity gap.
