A stock slingshot has three separate battles when pushed hard (over 70%) on the track.
Terrible Aerodynamics
Lack of rear traction
Awful brakes
The first one really only rears its head on the long straights, everywhere else the first two are far worse. But the big front fenders, you know those floppy dog ear things bouncing around by the front tires, actually create lift at speed and the open cockpit creates dirty air and drag. Those "canards" on the front lip, those are for telling you where the curb at the 7/11 is because they don't do anything else. When the speeds start to push anything over 100 MPH the aero of the sling is a huge hurdle.
The traction issue is more complex. The sling is WIDE at the front and fairly well planted across its front tires. It's stiff sway bar, meant to keep that back tire sitting flat, does a good job of reducing body roll. The biggest problem with a vehicle with three points of contact with the ground is lateral instability. It will want to Tip Over when pushed hard around a corner rather than slide. To keep this from happening Polaris did three things: They put the most mass over the axis between the two wheels (the motor), they placed the center of gravity as low as possible (about 13" high) and they made it very wiiiiiide. This works to keep it from flipping over but it comes at a high cost.
Low weight over the drive wheel at the rear.
The resulting lack of traction in the back creates a pretty bad oversteer situation. You can do a little to help this by widening the rear tire and mixing tire compounds front to rear to try to balance it out but it is never going to be ideal. An actual functioning rear wing can create some downforce but it would have to look like a McLaren Senna back there to get results that would do much good. The stock sling is fun at the track, sure, but when pushed anywhere near hard, the first thing that will pass you at the track will be the rear end of your own slingshot. Not trying to advocate for anything here but adding another rear tire really helps
Now back to that long front straight away..... the second or third time you hit it you may want to lighten up a little on the loud pedal because that middle pedal that is supposed to stop you is gonna be a little spongy. LIke, "holy crap that gravel trap is getting closer!!!" kind of Spongy. Again, a fourth one of those calipers thingies helps but even then whatever tractor they borrowed the front calipers off of was never intended to be a track tool. If you are going to track the sling once a year in group 3 or 4 get some GOOD pads. If you are making it a weekend warrior and want to be that pesky annoying guy in the mirror of those vettes and vipers in group 1 and 2 (mustangs will be behind you or in the grass. PS- I hate mustangs) then you'll want to get some real track brakes. Radial mounted calipers and rotors that look like a device meant to stop you, not looking like a little tin plate to eat you pizza off of.
You can have fun driving anything at the track and I highly encourage anyone to go. Even if you go as slow as possible track time will improve your driving skills and it is much safer than pushing past 70% on the road. No cops, no oncoming traffic (except for mustangs), lots of fun.
One of my favorite quotes for you, from F1 driver Martin Brundle:
Over steer is hitting the wall with the back of the car,
Under steer is hitting the wall with the front of the car,
Horsepower is how fast you hit the wall,
And Torque is how far you move the wall once you've hit it.