[slotloco]

I think tuning front engines slot cars well is possible, but usually more difficult.
Partly to get the weight distribution correct, but more so, dealing with the imbalances usually caused by the long driveshaft and spring system both Scalextric and Fly used.

In the case of Fly cars like the Capri. Mr Rafael Barrios Senior who started the company about 1992, had a very fixed opinion that the slot car should have the motor in the same place as the real car.
- We are so fortunate they modeled a lot of rear engined race cars !!!!

For that Capri, you will have to deal with the slop between the rear axle and bushes - usually some applications of thin superglue applied carefully to a lubricated axle, can be used to remove the slop.
Also, before bothering to go too far,  make sure rear the wheels are not at an angle on the axles, or you have too much uphill battle, and then you probably need replacement tyres depending upon your track situation.

Soft braid, and I think it has stub axles due to the front motor, so make sure the fronts are not carrying too much weight, and take off the front and glue and true the tyres, and coat with varnish or superglue as well to remove the grip.
It will need a lot of weight at back - about 15 grams.

It is possible to make it run nicely, but just not like a Sideways Capri. The "Racing Capri" version from Fly can be made to run really well, but needs replacement rear end even so.