Hi Dave .

Welcome to the forum from the UK

The ideal place depends on the rider - where is the most comfortable for them and of course where they can get most force for little effort .
The other concern is the seat because the legs do provide a little help in "staying put " whilst cycling.
IIRC there is one somewhere on the forum .

Here is a tadpole design for a chap that cannot ride a bike due to balance problems

regards from the UK