Having tried all sorts of ways to get the Match Height stacks to work in F6 using custom selectors I have found that the way to get this to work is by using Match Ids. In this case I have used them on the two sections of the card which might be variable because they contain CMS introduced text:

There are two Match Height column stacks; one for the top and one for the middle section. Here is a screen shot showing the middle rows:

OR

You can now use the equaliser swatch:

and just add the equalise class to each area which needs it. Has equalizer on the three columns.