found these work really well for holding 25mm and 28mm minis to the rubber steel plate in the GSW army transport bag.
i used 2 on the 40mm bases and a single on the 32mm bases, and while they do hold the mini (held upside down and given a gentle shake), i think the larger based minis might b a little close to the weight limit, so i would recommend adding one additional magnet to these bases or using a larger size