Breeding Boxers

Question
"Hi, we have two boxers, dog 5.5yrs, bitch 19months, she is on day 12 of her heat cycle and is very much teasing the dog and standing for him but not allowing him to enter her, she yelps so I suspect she is still very tender, the blood is still quite red but is changing.  My question is do we continue to let them try mating or wait another day or so, we don't want to miss out though.  Also our dog seems to be a little shorter in the hind than her and is having trouble getting there, what can we do to help? Thanks"

Answer
Absolutely do nothing and do not interfere.

She should be over 2 years old before breeding.

They will mate when it is right for her and her cycle and not until.

Man should not get involved as it can mess with her emotional and psychological state.