No size restriction but;

Dry weight is 15 kg. Applies to F4  C & H

So turbines can have a T/O weight of 15 kg plus fuel.

Same for a IC model.

Same goes for Electric Battery's, but if the battery's are removed for a weight test the radio must be working. (so the 15 kg includes a radio battery)

Atro's picture above is the model transport from the hanger to the flight line.

Thanks to Atro for the excellent photos and updates, keep going.

Control Line ~ F4B