It's a PITA. There is a steel tube just to the rear of the bulkhead that must be moved about 3 inches back. The side structure may be changed too. In addition, the inner panel under the rear cowl has a flat area that sits on the tube and the side panels sit on the side structure. Those would have to be changed or replaced. Lots of very unpleasant fiberglass work.
The other possibility is to do what we do on the FIA: Make a crossbar that is intersected by tubes that the roll bar slides into. There would have to be an angle that projected back to pick up the top edge of the new bulkhead panel.
And possibly other things that I haven't thought of.
