What's the story on these? Are they supported? Any real downsides with this conversion?

I have a friend with one. He’s active on mooneyspace, goes by aviatoreb. He loves it and is probably the guy you want to talk to. It’s a “rocket”

We maintained one for a while. The special rocket parts like the exhaust are a little difficult to get if you want a new one. Rocket doesn’t like to answer the phone. But the rest of the plane is standard Mooney with a TSIO520NB. Blistering fast. Like 200+ KTAS.

Check the useful load carefully. I was told they are single seat airplanes with full fuel.

Looks like it. A useful of 900 - 220lb pilot - 624lb (104gal) leaves 56lbs.

It's a flying gas tank.

that's not necessarily a bad thing. Think in terms of range, not gallons. If it had 30 gallons less fuel capacity, that is a 2nd person. But would smaller tanks make it a better plane ?

Looks like it. A useful of 900 - 220lb pilot - 624lb (104gal) leaves 56lbs.

It's a flying gas tank.

I believe all of the Rocket conversions got the extra fuel capacity, up from 72 or 74 (standard K) to 104 gallons. As always, fuel can be traded for butts or bags in the cabin as required. Two bigger folks in the front seat might bust the forward CG limits with all of the weight on the nose.

Byron is correct above... most of the airframe is still standard Mooney, and the engine parts are still pretty standard. Rocket does still support them, and parts like exhaust can be repaired by your favorite shop too. The cowl is custom, but fiberglass and repairable with standard methods if needed. They are heavier than a standard K model Mooney of course, and will consume rubber donuts for the gear faster, as well as brakes and tires.

One thing to note, since the engine package came from a twin (I forget which), the prop feathers. This could be a safety-enhancing glide extender if you lose the engine up high, but if you have oil pressure loss and partial power down low it might be a hindrance.

They climb like a homesick angel and go very fast, especially up high, and can go very far.

the engine/prop are from the C340. The full feathering on loss of oil pressure (not loss of engine) can also kill you. Imagine something lets go on takeoff. Now, instead of a minute or three of power to get around the pattern of find a place to stick it, you are engine out. There are reasons piston singles don't typically come with feathering props.

The Rockets are fast and climb very well. It's really the climb that will shave time off a trip and get you to the safety of a higher altitude quicker than an unconverted plane. It would seem obvious that the Rocket has the same LOP challenges as would a 340, but it cn be done.

Mooney was critical of the conversion to mid-body airframes, saying there was insufficient arm on the tail to balance that heavy engine/prop combo. Of course, they were selling a long-body with lower performance against it... With any mooney, a pre-flight inspection should include lifting the center section of the tail. If there is more than a little play, it is prudent to check the condition of that mechanism. This would be especially true of a Rocket.

The plane has a forward-CG issue that is often solved with a bag of sand in the baggage compartment, and careful consideration of real-life W&B for one's 90% trip is advisable.

The big prop doesn't have as much clearance as does the unconverted plane, and the heavy engine can be more prone to bring prop strikes.

It's not a good starter plane, but carefully flown, it is very, very fast.
-dan