Apparently some guy fitted a 737 apu to a jabiru!!
Could be done, but you'd need one hell of a reduction gear - you'd also struggle to get a noise certificate on it in the UK or Europe.
It had vertical climb capability, and a 25000 ft ceiling.
Sounds fairly realistic.
Due to the fact it cruises at such a height it can maintain 150kt indicated which equates to a 250 kt TAS (Ididnt check it on my wizz wheel).
Vne on a Jabiru is 116 kn IAS, so assuming that it's airspeed indication errors are roughly linear, that's about 30% above Vne, and in all likelihood beyond the design structural limits.
Also, 150kn CAS at FL250/ISA equates to 202kn TAS - not even close.
So considering it can fly at the height of a jetstream (which for the definition, has to be at least 60kts in magnitude, u can get a 300kt ground speed out of it.
Well, disregarding for a moment that there is almost certainly not enough spare mass in a Jabiru to fit the oxygen system you'd need....
Because it has beta mode if one was game, u can descend vertically. The hurdle will be getting it IFR certified.
You'd also have to try and get the duplicate instrumentation, transponder, VOR/ADF/etc - maybe is somebody would allow it as a single seater only, but certainly not 2-up.
Okay, maybe the 4-seat Jab 2-up !
G