"hiding" a multiselect field widget

Hi there,

I have a form in Flow Script (Cocoon 2.1.11) with many different widgets.

I use this definition in two different form templates--in one I hide 
some widgets, and in the other I hide some different ones.

All works well, except when I define a multi-select widget.

My definition seems pretty standard:
<fd:multivaluefield id="multi" required="false">
<fd:datatype base="string"/>
<fd:selection-list>
<fd:item value=""/>
<fd:item value="cat"/>
<fd:item value="dog"/>
<fd:item value="mouse"/>
</fd:selection-list>
</fd:multivaluefield>

I need to keep this widget on each of the two forms to preserve its 
value as the user clicks between forms without needing to save it to the 
database till they click a Save button.  In one form I need this widget 
to be visible, but not on the other.

But it does not "hide" when I try to hide it using: <ft:widget 
id="multi" ><fi:styling type="hidden"/></ft:widget>

I tried with Firefox 23.0.1, IE8 and it makes no difference.

However, if in the form definition, I change the definition to an 
ordinary list by replacing "multivaluedfield" by "field", then the 
styling command to hide it works correctly.

Is this a known problem with the multi-select widget, and is there a 
workaround?

Paul