Walls and Ceilings - Bottom edge

Another sheetrock question. I'm installing sheetrock on a framed wall that's built on a 9" high concrete curb. This is a garage. Due to certain "irregularities" in the curb pour (poor construction of the form, i.e., it almost collapsed as I poured), the curb slopes significantly outward toward the bottom - it's not vertical by a long shot and even has some artistic touches like freeform bulges. I was able to trim about an inch down from the top of the curb with a circular saw with diamond blade before installing the framing, but that's where vertical ends. As a result, I can't run the drywall even close to the floor and need a way to trim the bottom raw edge of the wallboard.

I bought some of that plastic stuff that seems to be for this purpose (U-channel or something) and my first question is how it's installed. Is there an adhesive or do I just install with the longer side on the outside and put screws through it into the bottom wall plate? I'm a little concerned that the edge is only about 3/4" and that puts me about 1/2" from the sheetrock edge - too close to the edge for a screw?

The other question is, when taping and spackling, do I incorporate the plastic channel into the finish? Will spackle stick to plastic? Or do I spackle and paint and put the channel on afterwards?

You may be surprised to learn that at this time I know virtually nothing about sheetrock installation.

are you saying that you want the dry wall to hang down,past the bottom plate to the floor?
are you running the sheets horizontialy?

No that wasn't what I was saying. I want to have the bottom of the sheetrock about level with the top of the curb, or a little below. That would give me a raw edge on the bottom of the sheetrock about 9" above the floor. Edge is raw because some sheets are installed vertically. I just want to cover and protect the bottom edge from bangs and make it look a little more finished.

'in my' opinion,-the sheets should run horizontialy.
the bottom of the lower 2x plate should be 1/2" inside the outside edge of the curb.so the sheet of dry wall is about flush with the curb.
if the total heighth of the dry wall surface is not 8'?
suggest 1st horizintal row,bottom at the bottom -1/4" lower than the plate 2x. then cut the next higher to allow 1/8" gap
at top & joint at lower row of sheets,to allow for mud fill with paper tape over 1st layer of mud.

this make 'any thing any clearer'-?

And to answer about the end caps, I have done what you are proposing and found that a bead of construction adhesive in the bottom of the channel does the trick. the long side, BTW, goes behind.