Face Based Host vs. No Host

I recently downloaded a family of diffusers that are face based. It bothers me because these diffusers connect to open ended runs of duct work that will vary in height throughout my project, therefore, they can not be inserted as face based. From everything I have read, it is not possible to change a face based family to a non-hosted family.

Does anyone have any ideas/suggestions/experience in recreating families like this so that they behave they way you want them to? I simply want to attach and connect this particular diffuser to an open end of duct work.

I attached the family that I am referring to.

Any help would be greatly appreciated!!!

Your options are basically to find/create a non-hosted family that fits your needs or to create workplanes for each mounting height and host your current family to those before connecting them to the duct. Or you could create a single workplane and offset the diffusers whatever distance is appropriate in each instance, assuming that family has an offset parameter.

Thank you for the suggestions.