Currently, most of my retirement savings are in a 401K in an allocation that approximates the VT allocation. I hold no bonds in my 401K or otherwise. I'm expecting to have a windfall soon, and was debating creating an allocation for bond exposure since my pre- and post- tax investment are all basically in VT. For context - 401k is currently \~$500K and windfall will be \~$1.5 million (all in after tax dollars). Tax advantaged retirement accounts will continue to be funded out of current cash flow.
I've read in various other posts here and on the broader internet that its not as efficient to hold bonds in an after-tax account. Does that mean that I should allocate 100% of my 401(k) to bonds since it will represent 25% of my total investments? Not sure if it matters or not for the question, but age is 40 and was going to throw the entire bond allocation into BNDX. TIA!