Here is what works for
my boat.
You want the boat to ride as low on the trailer as possible. Easier launching, loading and towing.
You should have your main bunks extended past your transom to support it.
Your front bunks should form a horizontal and verticle "V" matching your keel.
Front bunks: (hard to explain) but the front should be higher then the rear encasing the keel. This will help center your boat.

My
main bunks are verticle mounts, but yours should be about in the same place next to the outer chine.
Once I got the boat loaded on the bunks and the
Bowstop positioned for lenght, I moved the front bunks in position to match the keel.