front "nose" on Cougar buckling

That type of front cap is usually just the fiberglas skin without the lauan plywood backing. That is so the skin can be curved at the top and bottom. So, you have the interior paneling, then studs with probably batt insulation and finally the exterior fiberglas skin. The buckling or wavy appearance is the exterior skin sagging between the studs.

You can remove the exterior trim and then remove the fiberglas skin, then either add more studs or glue rigid foam insulation between the existing studs and reinstall the skin (or replace it with a new skin).

Another option is to remove the interior paneling inside the front closet and then reinforce the front wall, again either add more studs or install rigid foam, then reinstall the interior paneling with trim to hide where the paneling was cut.

I have seen some units where the front skin was reinforced in the flat area of the cap using either flat lauan as a backer or a thicker structure that looked similar to a hollow core door. That way the flat area would not have the problem you are experiencing yet the top and bottom of the skin would still curve as needed.

I don't understand, is it buckling as your thread title suggests or do you just wan't to change the shape?

FWIW, mine is pretty flat too and I don't think your going to effect its shape much by forcing foam in. I think all you would accomplish is making it lumpy and non-uniform.