Airshow/EOY Thoughts and the Stihl Sport Racer

It's been just over a month since the Air Races.  Truth be known, I'm just about out of photographs that I think are interesting.  There are still many worth commenting on, such as this one of the #30 Stihl Sport Class Racer.
The Sport Class definition:  Sport aircraft shall be any kit or amateur built aircraft that is certificated by the FAA and has completed a phase 1 flight test. Aircraft are to be powered by an internal combustion engine or engines totaling no more than 1000 cu in. and capable of a 200 MPH minimum qualification lap speed.  Stolen from here http://www.sportclass.com/.
The best of the Sport Class at the races moves over 380 MPH.  Relatively speaking, the air frames are small.  Let's see, on the list of elements to make photography interesting:  Small target, check.  Rapid movement, check.  Shutter speed limitation to catch prop blur, check.  And finally, rookie behind the lens, check.  Maybe the taxi photograph was the environment with the highest probability of a good shot?
Hold that thought.
Back to the photo.  It should be noted I liked this particular aircraft from the start.  It's orange.  And I am that shallow.  It's my first year at the races, a break here is required.  Anyway, Stihl is the primary sponsor and for that many thanks should be given.  Rumor has it, chain saws were given away on award night.  I can't make this stuff up.
As mentioned, this is on the taxi way.  The goal was to capture the propeller blur.  In the first pass, that goal was achieved.  And with the passage of time, this one shot represents to me why I need to go back next year.

ISO 100, f/20, 1/80 sec, 600 mm

All things considered, not a bad shot.  At the 600 mm focal length, general rules are the the minimum speed should be 1/600 second.  I had to slow the speed for the propeller blur.  The blur at 1/80 is right where I want it.  To get the speed that low on a sunny day, the ISO was as low as it would go and I had to go to f/20 aperture setting.  I usually like to shoot f/8 to f/11.  Optically best for the lens.  To get the 600 mm reach, I needed to shrink my sensor.  The D7200 has two sensor options.  The two sizes are DX format (23.5 x 15.6 mm) and 1.3x crop of DX (18.8 x 12.5 mm).  The DX format has a image size of 24.1 megapixels.  The 1.3x crop of DX achieves an image size of approximately 15.4 megapixels.  So what does all this mean?  It's all about the angles through the lens.  The lens I was using was built for a full frame sensor.  Because the sensor in the D7200 is smaller than a full frame, it has a different angle through the lens that effectively gives an extra 50% reach for the image.  Make the sensor even smaller, the angle changes even more, and I get to 600 mm out of a 300 mm lens.  But there is a penalty to pay.  A smaller picture.
When shooting nature subjects, the restrictions aren't as great.  For the most part - fast is good.  Light control - or contrast control is more important.  In other words, prepping for the air races by photographing birds didn't help much.  Well, for the jets it did - but to catch the prop driven aircraft I need a new tactic.
The simple answer is a neutral density filter.  I have a variable filter, but for good shots I need a better set up.  Good ND filters are expensive, so I need to figure out one or two filters.  Either way, I have to get better and more knowledgeable about using these filters.
The not so simple answer is what changes in equipment there might be in the future.  New camera, new lens?
The real answer - and the answer to most of the unfinished points raised here is I'm an amateur photographer.  To get to the next level is expensive, $4k at least.  I could upgrade  a lot cheaper, but that's not me.  But If I'm going to swim in the small pool I'm going to do it right.
And so the planning begins.......