Advice on sedum planting in rockpile?

Hello. I got this bright idea to plant sedums on the rocks near my porch. Years ago I dug all the dirt out of these 'revetments' down to ground level and replaced it with river rock. I was thinking I'd pull away the rocks from an area, make some 'pipes' out of concrete, fill them with dirt from ground level up to the top of the rocks, and plant sedums. After getting this brilliant idea and buying sedums, it occurred to me that since I know nothing about them other than they look really fine, I should probably ask someone who knows something before I go ahead. (How's that for addle-brained planning?). Some photos of the rocky area are attached. It gets about 5+ hours of direct sun from noon on. Zone 5b. The soil under all the rocks is well drained. Here's the sedums I bought from Lazy S:

Sedum kamtschaticum 'Variegatum' (2)
Sedum tetractinum (2)
Sedum sieboldii (Blue Form) (2)
Sedum sieboldii 'Nana' (2)
Sedum ternatum (2)
Sedum emarginatum 'Eco-Mt. Emei' (2)

The long 'upside down' area is on the side of the house and never gets full direct sun, except for an hour or so in the evening. But it does get a goodly amount of light and I was thinking the Mt. Emei would work there.

I'm very curious and eager to get started. Here are some questions I had:

1. Will the sedums grow beyond the 'dirt islands' made by my homemade pipes? I can't tell if they actually grown on rocks, or on dirt between rocks, or if different kinds do different things.

2. Are there any special dirt recipes I should use? Some sites talk about permatill and other specialty items. I was planning on using some bags of Scott's topsoil to fill the 'pipes.'

Again, thanks for any help!

Don't see why it wouldn't be fine for sedums. I'm not getting the point of the concrete pipes though... why not just push the rocks away, plant them in the ground, remulch around the crowns with the rocks. It would save a lot of what seems like unnecessary effort... unless I'm missing something?

Thanks for the reply. The rocks are 2+ feet deep. I could push some rocks aside and put some dirt in the "dip" for the sedums, but I'm concerned that it would also provide a home for weeds. The pipes contain the dirt, while allowing drainage through the bottom. Sure there'll be some dirt getting out, it's inevitable, but the less dirt for weeds the better, yes?

As far as dirt goes, all I can tell is a 50/50 mix of topsoil and perlite. Would that be OK?

Sedums are very easy to grow. I suspect you'll be successful with this plan.

Half soil and half perlite would be somewhat problematic... the perlite will float to the surface whenever it's watered. Regular soil would be preferable to that. As Tammy says, sedums are by and large very easy to grow.

I expect sometime in the future, you'll wish you'd just excavated all the gravel out and filled it with soil to make it a "regular" planting bed. If the gravel is really 2' deep, it will be tough enough to install the pots.

So, sounds like you plan to make the "concrete pipes"? This sounds problematic in itself. You're not a potter, I take it? If you are still planning on doing this (still sounds to me like a lot of hassle for a strange notion to me), why not buy masonry flue liners, rather than "making the concrete pipes"?
http://www.google.ca/search?q=masonry+flue+liners&client=safari&rls=en&source=lnms&tbm=isch&sa=X&ei=0Ru4U4SWO830oATg_YHwAw&ved=0CAYQ_AUoAQ&biw=1714&bih=990