I've come to the decision that with all the 6mm out there. And after spending a lot of time sanding/filing bases to fit GW and even other bases holes. I'm just going to filp the bases over and glue the figures to the underside/bottom. E.g. this Cmd Stand of mine using the original SM1 metal SMs ... A simple & workable solution, IMO ...
My next project interrupting my Chaos painting campaign, is to sand off the Trolls Under The Bridge square 6mm base on their figures. And glue them on round disc bases to match the others from various sources of 6mm including GW ...
Along with my rant on another thread here about model makers designing figures that poses are not gamer friendly and using fragile modeling material ... " Here's my main complaint with some model makes ... Thin ankles and and arms sticking too far out are not modelling or gamer friendly. I love the various poses ... some figures are an accident waiting to happen. I have figures with their arm sticking out from various makers. And those are hard to keep from breaking, even when painting in some cases. So one has to be very careful. Regardless a note to all model makers, I love detail ... but I don't like fragile. And some poses or weapons, etc. are just not strong enough to use with out concern. E.g. I've got some 6mm figs with potato masher/stikk bomm type weapons. I probably wouldn't use them to game with ... those would not last long on the gaming table, IMO ... "
So along with all that ... I'll add the round size/square base situation !
My Christmas Wish is for model makers to get their "poop" straight and make models more gamer friendly and useful ...