If you're wanting to have trees that are uniform for aesthetic reasons then it's not bad that you cut those on the border as I have done in my town. The only reason I had to put trees on borders was in a about 2 or 3 acres the river and a house takes up most of the space so I had no choice but plant on border. If you're going for the natural look then go ahead and plant them staggered and on borders.
I know I have one acre that has less than 12 trees (minimum amount for perfect acre) in an acre on the beach and I have around 11-16 flowers in that acre and I still have a perfect town rating for 4 weeks, currently starting 5h week.