Yes, I've done just this action on my Partner's A2. The surround is different for the smooth and slatted types. The slatted type will fit the smooth grill surround, but it sits slightly proud and doesn't make a perfect fit. The smooth grill needs to be reduced a few mm's on the sides to fit flush in the slatted-grill surround. It is obviously better to keep to the dedicated frame for each grill type. The only reason that I have swapped the two is because I have done some mods to my smooth grill and preferred the profile of the slatted-grill's frame. I wonder why you haven't used the correct frame around your slatted grill? I does have the better profile?
David