  We present a new design and assembly procedure of a large-area gas-avalanche
Resistive-Plate WELL (RPWELL) detector. A $50\times50 ~\mathrm{cm^2}$ prototype
was tested in $\mathrm{80 ~GeV/c}$ muon beam at CERN-SPS, presenting improved
performances compared to previous ones: MIP detection efficiency over 96\% with
3\% uniformity across the entire detector area, a charge gain of
$\mathrm{\approx{7.5 \times 10^3}}$ with a uniformity of 22\%, and discharge
probability below $\mathrm{10^{-6}}$ with a few single hotspots attributed to
production imperfections. These results pave the way towards further up-scaling
detectors of this kind.
