Brouwer M1811 grip magazine compatibility

I have a California sig p320 with the M1811 grip. The website says “ They must have the newer square peg base pads which feature beveled sides. The older round peg base pads will not work.”

I want to buy some second hand OEM sig mags but they’re rounded at the bottom, has anyone tried the older rounded mags? Will they absolutely not work and should I just pay the extra for new mags?