This depends I think. If you are dealing with a "production" builder that's putting out "volume" I'll bet you can negotiate quite a bit.
If you're dealing with a low volume, semi-custom shop, it's more about an on going relationship. Our boat was in this category, the contract was one page and a hand shake, and issues were resolved quickly during the building process at monthly meetings at the shop. Very little haggling, lots of mutual trust, and in the end some very good friends. We wanted them to stay in business, they wanted us to get a reasonable deal. Easy-peasey.
Morris is one of the few companies left, that value the relationship they create when they build a boat. There are a few more out there, but most production builders make and sell their boats like any other commodity.
My boat buying is typical of those production builders. I bought two used boats from the same dealer over the course of 4 or 5 years...who better to BUY a new one, than the guy who has come back for a second boat. You would think that I would get a phone call or email about new boat deals, this dealer has/had. Not even a followup call after buying either boat, let alone a sales call or invite to look at new boats. Take the money and on to another buyer...that is what we are...buyers.
They fail to understand that many of us are not buyers, we are owners. And the boats are more than a payment to us.
Enjoy the Morris, it is one of the best boats I have ever worked on and all owners I have met talk freely and candidly about what an experience owning one is. You are truly part of a unique experience.