There is quite a bit written about the training benefits of handling puppies during the early development stages.
Children have had it figured out since the beginning of time.
The U.S. Army calls it the biosensor method.
Have you tried it Dan? I have read up on it. Practice it to some extent but man you have to put some time into it on a daily basis. The theory makes sense. Kinda like the horse whisperer. Lots of daily petting and letting the dog trust you, when you lay them on their back.