Just planning my new hedge for October planting, I have a new house, completely open on all sides. Have decided to go for hawthorn/privet mix which are fairly fast growing. What is the best size to get balance between fullness (at bottom) and height. I have been quoted for 1.5m but worried they will be really straggly and I have heard that smaller plants will overtake more mature plants as their roots develop better. All inputs appreciated.