Bertram 20 Main chine hight at transom

Here is the same angle as the boat you posted. Looks the same. If you go square On That’s where you see it

 

Might be an optical illusion created by light and shadow, in any case, nothing you can do about it .

 

Yeah. That’s ok I’m fine with that. I was really just wondering what kind of impact it might have on the ride

 

Going to outboards is probably pretty common with these old boats today, but they have extreme vee for a 20 footer and tippy enough with a heavier sterndrive, that is my reservation about the idea.

 

I see some older fiberglass boats that have a slight rocker in the chine line, always assumed it was due to sag in the hullsides, especially in boats that carry a heavy cabin and sometimes a tower on the gunnels.
Molds shrink and sag, as well as the hulls that come out of them, so the original plug might have been arrow straight, while later in production the hook grew into existence.
A perfectly designed hull becomes functionally imperfect when exposed to variable external conditions such as sea state and loading, so a bit of compromise, as in a slight chine rocker may be a designed in as an attempt to deal with that.

 

I think it's more an optical illusion than anything else, looking at the stern quarter photo, it isn't apparent.

 

The porpoising has zilch to do with the chine. It has everything to do with the weight in the hull and the angle of the engines.

 

Chine flats can affect porpoising, but as you mentioned, other things are well involved.