I have a crew cab with the stock alpine under seat subwoofer, fold out platforms and the rear seat folding mod.
The stock sub fits under the fold out platforms without issue. I don't know if an aftermarket one would fit- I guess it would as long as it does not come above the lip of the under seat storage.
My dog isnt a huge fan of laying on the platform over the sub though- I imagine that type of vibration would be wildly unsettling for a dog- not to mention I wouldn't want to deal with that myself for any amount of time
If you look at the post from
@SitKneelBend the stock sub sits below the level of the hole so the folding platform would fit (as evidenced by having both in my truck) but the driver side kicker sub he has sits on top of that hole so the fold out platform would not work with that side