To reaching forward is about positive forward rotation of the hip on that side with the arm being close to straight. as my stroke and rotation improved I shortened the distance to the footrest which helps.
The top hand "push" is often a misnomer as it does impart a forward force but that is the rotation force of the torso/hip rotation, not an independant arm push
Don't bend your spine to lean forwards, bend at hips.
Many of us have short hamstring muscles and find this bending difficult. Stretching your hamstrings might be one of the best paddling techniques you will ever practice.
