Jen The Room-Filler page 4 (Patreon)

Okay, this is as far as I have drawn out visually.  I suspect Mimi here will introduce something to giant Jen to make her smaller-- under certain circumstances.  Maybe it'll be a joke or constant threat that Jen's always on the verge of returning to this giant size.

Mimi will the stable-size huge one- and Jen will have two levels, too big to fit anywhere and at least smaller than Mimi (if not down to a "normal" big).

I'm thinking the mechanism (that hasn't started yet because Mimi hasn't given Jen the any of the reversal options) that Jen is a smaller size unless she's turned on.  Also that her breasts are basically indestructible when they're growing back out to her giant size.  So it would take away any harm to her that she could hurt herself.

The alternative option would be she couldn't eat or drink a certain thing, or maybe seeing a certain color?

Whatever the result, Mimi will give Jen more than one option of items they were given to reverse things if they got too big, but Jen has gotten too big for any of the others to be an option that would get her down to a mobile size.

Like one might reduce her down 50%, but that wouldn't be nearly enough.  They also can't mix and match, so they have to go with the least desirable one, but it's the only one with the results they want.  Jen might suggest the down 50% to Mimi, but she'll say that she'll keep it, but she likes being huge.