the cars can handle as low as 2.5t but the problem is that you can't get the rollout to work and you will dump in less then 5 minutes.
Over here the pro10 modified usually drive with 7t delta's, 4.0-5.0t star or mamba max 7700 but even with a 7t delta or 4.0t star some drivers dump in less then 5 minutes. This is on big 1/8 gastracks.
They use nitro high downforce bodies like the porsche 962 and lola's to get the power to the ground.
In the pro10 10.5t which we have here in the netherlands as a stock class many use the medium downforce bodies like the nissan p35 or peugeot 905 to get more speed and less strain or heat on the motor. In germany they use 9.5t in stock. Speeds with a stock 10.5t on a track with 330ft straight will get as high as 55mph.
For indoors we use the 200mm pancars with 13.5t and 2s. This is fast enough for indoor use. In germany and swiss they also use the 200mm pancars outdoor with the 13.5t in it's own 200mm class.
Hope it helps you out