I see what you mean about lowering the drag. An internal calculation goes wrong because it calculates that with the given engine power and unbelievably low drag, the maximum speed is some insane number.
This is one of these issues with releasing a development editor. It doesn't matter when I'm the only one moving the sliders, as I simply wouldn't try to set near zero drag!
I think in your case you could try sticking to reasonable drag values, something like 0.3 would be OK, I guess? I don't know what the drag of a dragster is really but I'd guess it's not too different from an ordinary racing car. I don't know what sort of downforce amounts they use but the wings look quite big, seemingly a lot more substantial than a Formula 1 car.
About the top speed, there is a built in limit of 200 m/s. It's around 720 km/h or 450 mph. But according to Wikipedia, the fastest dragsters reach around 335 mph so that limit shouldn't affect you too much. To me it seems like tyre physics are the biggest problem the dragster faces at the moment.
I was thinking today how far we can go. I realise your dragster and some other vehicles have trouble with tyre physics limitations. But it doesn't seem sensible for me to delay the public release, in order to work on the old tyre physics. I've got a new tyre physics system in development and it seems as if that's where my work should be focussed.
For the mods support, there are quite a few bugs and issues to sort out and it seems sensible to me to make this a public release at that point, instead of going on trying to support every one of 100 features that 'so nearly could be supported' for the first release.