Hi Pitmix,
A few years ago I had a nasturtium motorhome (sleeper above the cabin) on a Fiat Ducato 2,5 TD base (cousin of the J5 / C25).
I was very surprised by the acceleration and top speed capabilities of this machine. however consumption! 11 l / 100 when driving cushy, up to 17 on the highway
In addition, nasturtium gives such wind resistance that overtaking a heavy vehicle can be treacherous. I had a fright while doubling a caravan: sharp acceleration to 95, and there sudden capping (due to the turbulence I suppose). Despite a long straight line I had to pound to fold before I take the car opposite (which had to drive fairly quickly anyway).
The driving position was designed for a delivery driver "foot to the floor", not for a family outing. After 2 hours of driving I had unbearable pain in my ankle from raising my right foot. Ditto for the left in town, the clutch pedal going way too high.
Ultimately I built a wooden foot platform. It allowed me to ride allowing me to ride with my feet on the floor but ... at 90 km / h. If necessary, the engine can be fully pushed, but the pin quickly enters the red zone
In addition, it allowed me to have a discreet volume of additional storage: you can never have enough.
During a control a gendarme threw a suspicious eye on the platform, then let me leave amused.
On the other hand I forgot to fix it: in retrospect, I realized that it could have got stuck under the brake pedal!
In short, I recommend this type mounting on a van, I have not thought of trying on a car.