Hey Karl,
My dad has had a TA04 for about a year and a half, and I used to race it for about 3 months. I raced it not long ago, and it seems ok, but its only has the standard Diff. in the front.
You say you tried the front one-way, and it caused more oversteer, I'm presuming that is purely down to the way you drive (no offence). If you have been used to racing with a diff, you may use your brakes, but if you use your brakes with a One-Way, it will cause the car to oversteer, as it doesn't brake on the front wheels. To solve this, the best thing to do, is to gently slow down coming into a corner, then just coast through with about half power. In a straight line you may slow down before the other car, but you will make up the speed through the corner, while the other driver is building momentum again.
I suggest you use a softer rear spring, we use Tamiya Yellow on front, Tam. Red on rear. Depending on the size of the track, you will have to change the toe settings appropriatly. If the track is relativly small, and doesnt include too many straights, I suggest maybe 1degree toe-out, to help with corners, if there are some straights, perhaps 0.5 toe-in to help stableize the car on straights.
As for the shock mountings, I would go for the second hole in from the edge on both front and rear on the shock mounts, and on the wishbone, go for the inner holes on the front, and the outer holes on the rear. As for tyres, Foams work very well for grip, or T-27's are another good tyre, not as much grip as foams though.
If you plan on getting some foams, I suggest you get softer rear tyres, this will give more rear-end grip. We use 40's on the front, then 37's rear. This is possible due to most foam tyre's being sold in pairs.
I don't think there is much more to do, perhaps look at the bodyshell you are running, Mazda 6, Dodge Stratus, Nemesis, Alfa 156, these are good bodyshells to start with. Most are good to use, as long as they dont have a overly flat front, like the RX-8. I noticed a huge difference between my old Volvo S60 and the Mazda RX-8. But apart from this, just try different things if you dont like how it is. The main key, is if you over steer, you need to soften the springs/spring tension on the rear, to make it softer, if you are understeering, try tightening the shocks. unfortunatly, most things come with trial and error.
Apart from that, just try playing with gear ratio's, perhaps watch to find a car that you think would be a suitable speed for you, and then go and ask them what gear ratio they use. In the back of your instructions should be a chart with the pinions and spur gears, where you can find a suitable ratio.
If not this is how it is listed in the Book:
Spur
Pinion.id="beige">112T.id="beige">120T.id="beige">128T
34.....id="beige">-......id="beige">-.....id="beige">8.03
35.....id="beige">-......id="beige">-.....id="beige">7.80
36.....id="beige">-......id="beige">-.....id="beige">7.59
37.....id="beige">-......id="beige">-.....id="beige">7.38
38.....id="beige">-......id="beige">-.....id="beige">7.19
39.....id="beige">-....id="beige">6.56...id="beige">7.00
40.....id="beige">-....id="beige">6.40...id="beige">6.83
41.....id="beige">-....id="beige">6.24......id="beige">-
42.....id="beige">-....id="beige">6.10......id="beige">-
43.....id="beige">-....id="beige">5.95......id="beige">-
44.....id="beige">-....id="beige">5.82......id="beige">-
45.....id="beige">-....id="beige">5.69......id="beige">-
46.....id="beige">-....id="beige">5.57......id="beige">-
47.....id="beige">-....id="beige">5.45......id="beige">-
48..id="beige">4.98...id="beige">5.33.....id="beige">-
49...id="beige">4.88......id="beige">-......id="beige">-
50...id="beige">4.78......id="beige">-......id="beige">-
51...id="beige">4.68......id="beige">-......id="beige">-
The lower the number, the more acceleration you are going to get.
Hope this helps
Tom
P.S. I tried to make the chart straight, but it was very hard so thats why its a bit wonky []
