Hi Bob,
I’m not aware of a rule of thumb about how far open a hood should be. I guess “common sense” would come into play here. If the hood settles down so far you can’t even get your head under it, I’d say there’d be some points lost.
As for having a hood prop in the engine compartment, I’d say no way. My suggestion would be to take it out for the judging. Just like you'd take your cleaning, detailing, polishing supplies, etc. etc. out of the trunk and put them behind the car or on the perimeter of the judging field.
Hope this helps til an expert comes along with a more detailed answer to your Q……
Bill.
