Back in the days when the car was actually new, compared to its opposition it was always competitive on high grip tracks. It's a simple chassis with a natural good and nice balance but there's something with it which really makes it excel on high grip. The better the grip, the more edge it had, at least that's my experience. I wasn't good enough technically when I ran the car to really understand why, but there were definitely a few ocassions when I simply had an edge because of the car, it was just a matter of not making a mess out of setup or driving and then the win was pretty safe. Particularly indoors and on grass. I also tend to think that its official results support this - Jamie Booth won the BRCA national title with the Manta Ray back in 1991, and they ran quite a lot of grass and astro turf events already back then. Even in 1992 with the Top Force the GB team were at its best on high grip tracks, like Southend where Lee Wright was TQ and came really close to winning.
From my memory, it was never as competitive on really bumpy tracks or on very slippery tracks. Lack of slipper could've been one reason but I don't think it was the main one - the Yokomo Works 91 and 92 didn't have one and certainly didn't suffer too much. Lots of steering scrub, limited rear toe-in, no rear anti-squat, and quite short suspension arms in general might have contributed more. Plus the fact that the rear gearbox assembly isn't really up to scratch - it's entirely out of plastic, carries the whole rear end of the car with the suspension arms mounted directly onto it and despite its wheight it's tightened up with only four bolts in total. If you look at the TRF411X which - supposedly - is close to what Tamiya felt was needed to improve upon the Topforce, one of the biggest changes is that the rear arms were mounted on their own brackets on the chassis instead of sitting directly on the gearbox. It also had slightly longer suspension arms and close to equal length arms front & rear (Top Force has quite a big difference). Furthermore it had more 'modern' style differentials which the Top Force badly needs, which is even more obvious with the power available today..
Anyway - great car and it's been lots of fun driving one again lately. Only been able to do a few laps indoors so far but straight from the start it's been agile and quick, changes direction sharply and is nicely balanced. It's very forgiving and has quite a large setup window, can easily be driven both softer with more roll and downtravel or more firm/stiff settings.