There is another possibility.
I've seen pix of the GE T58 (or RR Gnome) - a free-turbine engine - with the free turbine amputated and replaced with a straight nozzle. Some extra fuel was injected into the new tailpipe - mostly for the dazzle factor - but without a variable exhaust nozzle, it a far-from-optimum a/b.
Presumably similar surgery could be executed on a PT6.