Please give the full model name of the boat you are discussing that you describe as a 2019 MONTAUK. Without knowing the size of the boat, judging if a 14-inch-tall WHALER decal would be appropriate is going to be impossible.
I don't recall any illustrations of a c.2019 Boston Whaler boat with a big red WHALER decal on the hull sides. In the classic era, the factory offered the option for a big WHALER decal. I don't see that option available on a new boat like a 2022 190 MONTAUK. That might be something you could make an inference from.
vtbw wrote:I am debating adding a large WHALER decal...
Regarding applying those large WHALER decals to the hull sides: I am not a big fan. I think the big WHALER decal is a bit too much. Of course, that is a personal decision. Also, I think the placement is going to be very important to get the correct look. Phil's suggestion to experiment in with the design using a graphics program is good advice.
Putting that big decal on the hull side is going to draw huge attention to it, and the decal needs to be carefully placed to get the aesthetics and space with other graphic elements on the hull correct. The overall size is also very important. If the decal is going to be big, it needs to be the right big size. There will be a fine line between just the right size, too big, and not quite big enough.
I am very sure that if Boston Whaler still offered the big WHALER decals as an option, there would have been considerable thought and discussion about the font, the size, and the location for the decal on the hull by their design department. When done right, the big decal can look good, but it won't be a case of any size, any font, any placement will produce a harmonious outcome.
For me, the Boston Whaler boat hull lines and its graphics have always been a fusion subtle design elements. Improving on their classic good look has always been difficult.