Increase stocks as part of a change in strategy
As part of a change in strategy, a portion of the family portfolio is being earmarked as long term/legacy, and for that portion, the allocation of stocks is being increased from 30 to 50%. The portfolio follows a slightly modified version of Taylor's 3 fund portfolio (VTI and VXUS in about equal weights, plus BND and VCIT, in about equal weights with a bit of HYG.)
Given the state of the markets, which the family considers to be overvalued, specially in the US, what strategy would this forum use to increase the equity portion? A lump sum change or slowly in the course of a few months. I would appreciate your input, if possible giving the reasons.
By the way:
VTI = Total US stock market.
VXUS = Stock market outside the US (developed + emerging.)
BND = Total US bond market.
VCIT = intermediate US corporate bonds.
HYG = high yield bonds.