https://imgur.com/a/4EhVRVP pretty sure that these smaller bases will not be acceptable in a tourney, but i don't care about that stuff, yet. as you can see, models with sensible stances or r simply smaller fit snugly in the 20mm bases. this also allowed me to cram as much models in a small figure case w/o the stock bases getting in the way. jsyk, none of my models touch even after wiggling each one. i'm quite aware of the movement disadvantage of smaller bases, but a smaller cylinder silhouette will let physically thinner/smaller models to peak around a corner with smaller base exposure. smaller bases with metal minis r easier to tip over, but this is not a game played with tilted/sloped terrain afaik. tags and bots r also on smaller bases, and bikes'll be on ovals/pills if i ever get any. what do u guys think?
A unit's base base dimensions are part of their rules. The silhouette rules specifically say that silhouette is keyed to the size of a unit's base. If you give it a different, non-standard base, you're departing from the rules. This is true for both tournament and non-tournament play. You're welcome to do it, and an opponent is welcome to be okay with it. But you'd still be playing a non-standard version of the game, and therefore would need your opponent's permission, regardless of whether it's ITS or non-ITS format. You'd be in a position where you're breaking the rules every time you put those minis on the table, and that feels like way more trouble than it's worth.
If you want the smaller bases for transport purposes you might want to consider using thin disks the correct base size that attach to the bottom of the base with magnets.
disks underneath the non-standard bases is what i thought of using, as well as upside-down gw 25mm ones (slightly smaller than stock).