and of course Access wants to keep the webcontrol on top even after I send it "to back".
that's more to do with standard access functionality. Simplistically a form does not consist of a series of separate windows - it's displayed as a single image, the layering of controls being part of the design. The magic happens when a control get the focus. At that point it becomes a window in its own right and it's z-order within the form is set to 0
As a simple test have two controls, one partially hidden behind the other. When you click on the partially hidden one it displays on top of the one that is designated 'on top'.
Subforms do not have a gotfocus event so the control does not get the focus - the underlying form does.
issues include the fact that the user may want to move the primary form around ... but will end up moving the invisible one.
not with the right coding. You can have code in the main form move event to move the invisible form to keep it in the same place over the main form and you can set the invisible form to no borders so user cannot move it on its own