Pilou... if what makes the brick are legal, then yes. ;-)
I hate these new toilets that use less water. The just never flush right.
Here in north Florida we are sitting on an aquifer with 3000 tera-liters of an endless supply of water. Sure it makes sense for most of the country that gets their water from reservoirs, but here, conserving water is like making soup to stretch a piece of meat while dining at an all-you-can-eat buffet.

Felix... I get what you were talking about. I'll often make both solid and open surfaces without regard to which is which.
But I imagine if you make the open surface, you can Flow it easier - then when you are done with distortions you can find ways to make the remaining object a solid but constructing final surfaces. Not an easy task sometimes.