It is perhaps my over cautious nature to such things but I used 4 jack stands to support the front end on my car when I started the engine and tranny pull. Im sure what you are proposing should be good, but I was concerned about all that weight. I was just going to put the jack stands at the jack points under the doors, but all that weight free hanging like that gave me pause. So I used 4 stands put right at the mounting points for the cradle.
'Course, now when I go to pull the cradle that will have to change but there also wont be all the weight there either with the engine and tranny out. But again, Im over cautious about such things, so keep that in mind as well.