on a 19 foot aluminum boat with riveted hull, are your bunks lined up so there is a row of rivets on the bunk or are the bunks in between the rows of rivets ?

I wouldn't want rivets on top of bunks. I would think it can't be good for the rivets over time. Even if it doesn't hurt them, at the bare minimum it would absolutely not be good for the bunks and especially the carpet.

My boat is only 17 1/2', the bunks are between the lengthwise strakes. That would put them in contact with rivets. It has worked without damaging rivets for years.

I was thinking if the bunks are between the rows of rivets that it would not be supporting the boat under the length wise runner in the frame work. would that be right ?

When I bought my Alumacraft TS 185 in 2004 I told the dealer I wanted a custom, 4 bunk trailer. He said he used Bear trailers and since their location is close to where I live I went and visited with them. They said they receive CAD drawings from the boat manufacturer showing where to place the bunks in order to give the boat proper support. And yes, there are rows of rivits under each bunk and they do wear the carpet some. But the boat loads straight every time and pulls easily. I doubt there's a custom trailer made for any rivited aluminum boat where the bunks wouldn't be in contact with at least some rivits.

b2

on a 19 foot aluminum boat with riveted hull, are your bunks lined up so there is a row of rivets on the bunk or are the bunks in between the rows of rivets ?

It doesn't matter.
If it is a 2 bunk trailer...the bunks need to miss any keelsons and be roughly equi-distant between center keel and chines.
On a four bunk... they need be postioned to miss any keelsons.

Here's an under-the-floor pic I stole from the Alumacraft site. If you look closely (I know it's fuzzy) the stringers run fore and aft, from the hull to the floor level. I have intentionally placed my bunks under these stringers (as indicated by where the rivets are) rather than between them, so the bunks are under the strongest part of the hull. Kinda like a floor has more bounce between the joists, rather than directly on them.
HRG

It doesn't matter.
If it is a 2 bunk trailer...the bunks need to miss any keelsons and be roughly equi-distant between center keel and chines.
On a four bunk... they need be postioned to miss any keelsons.
I am not familiar with keelsons
by the leelsons do you mean the row of rivets where the stringer is located ?
the hull I am asking about is a 2003 starcraft super fisherman 190

Bunks go to the outside of the strakes by roughly 1/2". This allow the boat to center itself when being loaded on a trailer. Take a look at any custom trailer. That's how they do it.

BTW, What's a keelson?

I don't believe my boat has strakes on the outside of the hull. There is a center keel and the the reverse chine on the outside edge with nothing in between except for rows of rivets.

I don't believe my boat has strakes on the outside of the hull. There is a center keel and the the reverse chine on the outside edge with nothing in between except for rows of rivets.

Then I would position the bunks under the location of the stringers. If you have no way of knowing exactly where the stringers are located, then merely place the bunks 1/2 way between keel and chine.

I am not familiar with keelsons
by the leelsons do you mean the row of rivets where the stringer is located ?
the hull I am asking about is a 2003 starcraft super fisherman 190

"Keelsons" are any keels on the bottom that are not the CENTER keel.
Not all boats have them.
Some people call them spray strakes, or just (more) keels.

Thank you to everyone who answered me and helped me I appreciate your help