Galactic charged cosmic rays, notably positrons, antiprotons and light antinuclei, are powerful probes of dark matter annihilation or decay, in particular for candidates heavier than a few MeV or tiny evaporating primordial black holes. Recent measurements by PAMELA, AMS-02, or Voyager on positrons and antiprotons already translate into constraints on several models over a large mass range. However, these constraints depend on Galactic transport models, in particular the diffusive halo size $L$, subject to theoretical and statistical uncertainties. Using Be/B data on top of the secondary-to-primary ratios Li/C and B/C, we have set new constraints on $L$. We have derived an average value of $L=5^{+3}_{-2}$ kpc at $1\sigma$. These constraints improve by a factor of 2 when low-energy $^{10}$Be/Be and $^{10}$Be/$^{\,9}$Be data are included.

Using these results, we have updated the so-called MIN-MED-MAX benchmark transport parameters that yield generic minimal, median, and maximal dark matter produced fluxes. We define these benchmark configurations from a selection of models based on the diffusive halo height $L$ and on a specific low-energy transport parameter that depends on the cosmic-ray transport scheme. We illustrate our results with a 100 GeV dark matter species annihilating into $b \bar{b}$ quark or electron-positron pairs, and present the positron and antiproton fluxes that these particles generate at the Earth. With our revised MIN-MED-MAX benchmarks, the uncertainties on primary fluxes reduce by a factor of 3-4 (positrons) and 5 (antiprotons) with respect to their former version.