On further thought, we need to back up on this topic. Unless the subject cabriolet is of late production, it likely will have the same chassis frame as the majority of the '32s produced. If that is the case, there is decent probability that the frame above the rear axles housings is already distorted from the car bottoming out and the axle housings acting as fulcrum. Apart from a weakness in the frame above the axle housings (later addressed initially as a service campaign to add reinforcements on the outside of the frame directly above the axle housings and ultimately in production with longer reinforcements added to the inside the frame rails along with shortening of the rear cross member to accommodate the thickness of the reinforcements), the combined weight of a full gas tank and a spare tire and wheel created the leverage of sufficient force to bend the un-reinforced frame rails.
That throws into question why Ford would release a luggage rack in Europe that would only increase the tendency for the frames to buckle at their high point? Maybe Europe had at that time such good roads that there were no pot holes for a serious jounce of the suspension. Or maybe their unique luggage rack wasn't released until the frame problem had been fixed.
In any event, if the subject cabriolet doesn't have either form of frame reinforcement, adding a luggage rack plus adding luggage, etc. to it, heightens the risk of damage to the frame and as islow points out, the most feasible route may be to relocate the spare tire to one of the front fenders. So, surreveps, I suggest that the first step is to determine which version of the chassis frame is under your cabriolet body.
