There were two very interesting developments at McLaren during US Grand Prix practice. Although fitted to the 2016 car, both may be pointers towards developments for next year, with a new front wing appearing, as well as a comprehensive sensor set-up at the rear of the car.
McLaren has gone for a very different direction with its new front wing, with the way the wing meets the endplate being an almost retro-style 90-degree joint.
In recent years a trend started by Mercedes has led to the wing joining the endplate with an arched section, to create a strong vortex to push airflow around the front wheel.
This new design does not suggest it would create such a strong outwash around the tyre. Either appearance is deceptive or McLaren is now following a different aero philosophy, not requiring the outwash.
This may be related to the 2017 rules, and opportunities for bargeboard and other aero devices along the side of the car to influence airflow.
Currently teams want to push the front-tyre wake out away from the car's bodywork, to prevent it upsetting the diffuser and rear wing performance.
They do this with the outer section of front wing, creating an outwash to push the tyre wake further from the car.
However, this approach is partly due to the lack opportunities to fit bodywork to control the tyre wake, the complex bargeboards being banned back in 2009.
Now that this area is freed up somewhat for 2017, perhaps McLaren feels the new bargeboard area is so influential that the front wing can be simplified to reduce the outwash effect and therefore also drag.
As much as the wider 2017 cars will look very different to this year's machines, there is still much to be learned from the current cars that can be applied to the new ones.
McLaren conducted a number of aero tests on the MP4-31 with 2017 developments in mind.
These tests focused on the rear end and appeared to be related to bodywork stiffness, with four changes made to check that.
Firstly, the bodywork around the rear wing mount and exhaust had a chequered pattern material stuck to it, with two sensors focused on this area.
These sensors were oddly fitted to the outer end of the suspension's upper wishbones, such that they would move relative to the bodywork.
This seems a less-accurate method to monitor any bodywork flex around the rear of the sidepods, but may simply be the most convenient spot to locate the sensors without unnecessary bolt-on rigs to hold sensors in a more suitable place.
The other testing add-ons were two stays supporting the trailing edge of the diffuser.
These passed from the rear crash structure rearward and outward on the upper rear lip of the diffuser. In this position the rear edge of the diffuser would be much stiffer than usual.
McLaren then fitted sensors in small, fin-shaped pods on top of the floor, looking down through the floor at the ground.
These are most likely sensors to detect any flex in the floor, by sensing any change in ground clearance of this specific floor area relative to that measured by other rideheight sensors.
In combination, this four-part set-up might be checking that any movement in the floor isn't reflected in accompanying movement in the rear of the sidepod bodywork, to which it is attached.
With the floor being subject to even greater loads next year, due to larger diffusers, any resulting movement of other bodywork may adversely affect the car's aerodynamic performance.
SAUBER FOLLOWS MERCEDES WITH CUT WINDSCREEN
A feature often overlooked on an F1 car's design is the small windscreen fitted to the front of the cockpit. This isn't a performance aero part per-se, but rather one designed for driver comfort.
At speed, the driver's head is both lifted and buffeted by the air flowing over the open cockpit and helmet.
To offset this, the drivers fit spoilers and lips to their helmets, plus they also run with a tiny screen fitted ahead of the cockpit opening.
The shape of the screen will define the level of lift and buffeting felt by the driver.
Often the top of the screen is either straight or curved, however Mercedes for several years now has cut four "V"s into the top edge.
Initially this design was run just by Nico Rosberg, who found the airflow characteristics suited his seating position and Schuberth helmet, whereas team-mate Lewis Hamilton - with an Arai helmet - preferred an uncut screen.
When Hamilton switched to a Bell helmet in 2015 he also adopted the cut screen.
Now Sauber has tested a version of the cut screen on its car, the white opaque test screen showing that the view through the screen is not as important as the airflow spilling off it.
WILLIAMS TWEAKS ITS FRONT WING
A small but influential update was made to the Williams front wing for Austin, with an increase in the number of fences under the wing.
Typically running two fences, for this race the wing now features four.
These fences are used to straighten the airflow passing between the front wheels, and in doing so offset the tyre squirt from the front wheel that would otherwise interrupt the front wing wake forming and reducing downforce.
Increasing the number of fences helps clean up this airflow area, but can make the flow more sensitive to the angle the front wheels are steered at.