@bisco ,
"Good question! I've often dreamed of building a super fast plane just for fun.
In theory, as long as you stay below the weight limits and respect the local rules (like flying by sight, not too high), there is no real official speed limit for scale models.
But the faster it goes, the riskier it becomes for others... and for your plane.
And in the event of an accident, the authorities may laugh less if it goes all out.
Personally, I aim for the maximum speed that I can control without losing the signal or the sight.
This is where the real challenge begins!
Let us know if you're building a car, I'm interested!"