DotNet Custom Control Design Time sizing Grips

I'm creating a custom control which contains a standard combobox plus a standard button. The control will offer alignment options for the button to the left/right of the combobox, or, above/below. the height will be restricted, in the case of button left/right alignment, to the standard height of a combobox, in the case of  top/bottom to twice the height of a standard combo box.
I've handled all that in the OnResize override for the control.

What I would like to do is restrict the display of sizing grips in the design environment to the left/right grips, losing the top/bottom and corner grips (as with a standard combobox, or single line text box) so a user gets a visual indication that the height of the control is not changeable.

A google search found only one item which would seem to answer my query (on your site - which is why I've bitten the bullet and signed up for, at least, a trial).

The answer to the question on your site leads to a broken link on another site.

Does anyone know if it is possible to take this much control over the appearance of a control in the design environment?

From a rudimentary search though the standard dotnet objects I can't find where the change is between a listcontrol, which appears to have a full set of sizing grips, and a combobox (which inherits listcontrol) which only has the left/right grips.