Over here, the council defines a 'parkflyer' (ie one we are legally aloud to use in a park) as electric, under 1kg (2.2lbs) and under a meter wide .... that said, there is a really nice little underutilized park round the road from home where I fly my 3.6kg, 1.35mtr rotor diameter nitro burning heli often ..... only time I ever had a council worker come up and ask me about it was to state how nice it was, and just how much was it to buy one!!