So I'm doing a build in my 2003 Dodge Dakota crew cab of 2 15" icons and would like to reinforce my roof. I'm getting 3/4-1" flex on one 10" incriminator I series and also headliner slap and it drives me crazy. I have a bulk pack of dynomat extreme I got for like 20 bucks. Would 3/8" MDF with kerfs And lots of pl then dynomat between headliner and wood be good? Just want to cut down roof flex and stop headliner flex. Any suggestions? I would rather not have to order stuff if possible as I'm tearing truck apart this weekend and shipping is slow

Thanks

Fiberglass the roof

The kerfed mdf should help, then as Julian said use some fiberglass.

Ok Thanks, so the fibreglass would obviously go on top of the mdf, between the mdf and the head liner? Would that stop head liner slap or should I use something in-between fibreglass and head liner? (insulation, dynomat or another suggestion?)

^{no, on the inside of the roof, fiberglass the inside between the headliner.}

^{Use a lot.}

^{no, on the inside of the roof, fiberglass the inside between the headliner.}

^{Use a lot.}

So Skip the mdf and make a fibreglass layer bonded right to the metal, just making the roof thicker and more rigid than the crappy tin roof? Or are you saying have metal, then glue on kerfed mdf, then fibreglass the bottom (inside) of the mdf on the inside then head liner?

^{no, on the inside of the roof, fiberglass the inside between the headliner.}

^{Use a lot.}

So Skip the mdf and make a fibreglass layer bonded right to the metal, just making the roof thicker and more rigid than the crappy tin roof? Or are you saying have metal, then glue on kerfed mdf, then fibreglass the bottom (inside) of the mdf on the inside then head liner?

The more mass you can add the better.

^{no, on the inside of the roof, fiberglass the inside between the headliner.}

^{Use a lot.}

So Skip the mdf and make a fibreglass layer bonded right to the metal, just making the roof thicker and more rigid than the crappy tin roof? Or are you saying have metal, then glue on kerfed mdf, then fibreglass the bottom (inside) of the mdf on the inside then head liner?

Correct me if I am wrong but I believe you use fiberglass resin and mat to strengthen the kerfed mdf. I have not seen anyone use only fiberglass as I would think that It would be likely to also flex. (Unless very thick and very ex$$$pensive)

Ya I decided to just do basic deadening and try it. Put up a layer of dynomat and then camper foam between headliner and roof. Helped a TON! Still have flex of course but the roof doesn't pop and sound like tin. And headliner doesn't have much audible slap hardly at all even with 2 15" icons. I know it could be a lot better but was amazed how much just what I did helped.

Ya I decided to just do basic deadening and try it. Put up a layer of dynomat and then camper foam between headliner and roof. Helped a TON! Still have flex of course but the roof doesn't pop and sound like tin. And headliner doesn't have much audible slap hardly at all even with 2 15" icons. I know it could be a lot better but was amazed how much just what I did helped.

Pics? Glad to hear it helped!