Disclaimer: I've never driven a Honda Acty in real life, so I can't comment on how realistic this mod is, only how fun it is to drive.
And it's a ton of fun! The thing about these kei vehicles is, they always seem to feel really fast despite their actual lack of speed, at least in games. That's a characteristic the Acty truck shares. It's genuinely fun to drive: sharp cornering due to its light weight, and some lift-off oversteer to spice things up. There's a ton of body roll, but never so much you feel like you're gonna flip. Quite the opposite: I once ran over a really steep hill on the inside of a corner, and the Acty handled it perfectly. It wasn't even close to flipping.
Others have mentioned the terrible fuel economy, and by default, the economy is really terrible, to the point that it seems super unrealistic. The point of these kei vehicles is to be as economical as possible, yet it only took me around 45 minutes of highway driving on the Shutoko to almost run the poor little Acty out of gas. Digging around in the files, I was able to find the [FUEL] section in /data/car.ini and change the consumption value from 0.00700 to 0.00070 - effectively reducing the fuel consumption by 100 times. Now it seems a lot more realistic given the engine's displacement and the car's weight. If you decide to try this car, I would do that first. Still... totally worth it.