CSS Sizing

If all else fails you can always use a raw CSS string can be used to size Miwi components.

<Box width={`75%`} height={`50px`} fill={`red`} />

Note: Sometimes CSS doesn't play nice with Miwi, or sometimes CSS just has bugs that are so old browsers have to keep the bugs around. So use CSS with caution because it won't always work with Miwi the way you expect it to.