Question about DIY rocks

I am going to attempt to create some rocks using the quick lite hydralic cement method as I read about in another forum, I might create a wall on the back of my tank.

I think I am going to use some combination of hydralic cement/CC/argonite sand depending on the use of the rock. According to antother thread(which seems very reputable) it will not need to be cured.

I have a few ideas about how I am going to set it up, but I have two questions and would like to hear about others experiances using this method.

1) Should I keep DIY live rock in a particular ratio to real LR to ensure proper potential for fitration and can this be offset by creating the DIY rock a certain way(sure as increasing it porosity).

2)are there any particular reasons not to have a Created rock backing on the tank other than aesthetics?

Thanks for any advice.

In a thread I was reading, a fellow stated that by using a certain type of concrete called something like "light hydralic cement" that was polymer based(I think), one would not have to cure the rock.

In the thread the gentleman stated using the cement to make reef backs for tanks and adding them right then to the tank without any curing. he said something about that using portland cement is necessary to cure but with the polymer based type curing wouldn't be necessary. He seemed to be knowledgeable about it, I was lead to the thread on another forum from a post on this forum.

Do you mean epson salt? is that rock salt?

have you heard of using pasta or other things to increase porosity?

In the long run, will optimal DIY rock have comparable filtration capacity as premium from the LFS?