One factor on increasing the number of strokes is an increased probability of crossing one of the previous strokes, although this may perhaps result in longer lasting pain and bruising/blood blisters in the aftermath.
I am not sure any of us believes in the “five bar gate” much featured in fictional writings.
At my school the Head seemed to go for covering a wider area (including upper thigh) as the number of strokes increased. I know some caners would go for “tight grouping”…I would have thought numbness might then be a factor.
Certainly in junior school hand caning anything more than two strokes on the hand didn’t seem to have much effect due to numbness.
Yes, bent over some object would be much easier to sustain, especially if held down.