The radius of a turn is equal to the mass times the velocity squared divided by the force. So there are three basic ways to decrease the minimum turning radius of a model. Decrease the mass (W/g). Increase the force(lift). Decrease the velocity. There are limits to how much one can decrease the weight, increase the lift and decrease the velocity. Measures that improve one of the three often adversely affect another of the three. This leads to a conflict of objectives. That is one reason why design is a creative synthesis rather than an analysis that can be accomplished with one pass through a spread sheet. A spread sheet can be very useful in analyzing a candidate design. Then its performance can be compared to another candidate design to see which balance of conflicting objectives fulfills the mission best or is the most pleasing to the designer. The process of design modification, analysis and comparison can be iterated until the designer is satisfied or, tires of the process.