UHD quadrature sampling help

We have a number of old flowgraphs that take advantage of quadrature
sampling and work fine in USRP1 non-uhd, but once converted to UHD (for
USRP1 and 2), we’ve been wholly unable to come up with subdev specs that
work- the I and Q are not synchronized in any way and any change in
frequency changes the relative phase between I and Q. The main
flowgraphs we’re trying to convert are Charles S.'s VNA and related
flowgraphs from gnuradio experiments . Can anyone
offer some proven working flowgraphs, or reduced version of them, for
UHD that depend on quadrature sampling at the USRP (LFRX or BasicRX) as
an example to us?