Underbody paint advice needed

Dynamat and spray-on bed liner? Sounds heavy. And not in a Marty McFly/Doc Brown sorta way.

When I did mine I painted all the structural parts (frame rails, etc.) and undercoated the sheet metal. Overspray was had but it's a black car so I didn't have a problem with that.
Not really you talking a few liters of paint be lucky if a few kg, the dyno matt would have a little weight but the difference it makes is amazing. I remember when i did my first angry car with it, my feet used to sweat from the pipes heating the floor up, it stopped that and just the road noise it cut out was massive. I will have 550-600hp so few kg isnt an issue