I starch the top moderately - my regular mix of starch to water. I starch the back heavily with a 1:3 ratio. Recently I was showing the my daughter how to do the Sharon Schamber thing and she commented that she didn't like the backing fabric because it was too stiff. No, sweetie, it's starched and I've never had a pucker.

THe SID foot has a small piece extending underneath the center - it is sort of like a plough that runs in the ditch. I'm not sure why you couldn't use it. However, the purpose of the walking foot is to keep the layers moving at the same speed and you won't (or shouldn't) have shifting between the top and the backing.

I agree with the others that it is not necessary to do SID stitching before FMQ. Just make sure you do a good job putting the sandwich together (nice and taut) and baste well.

The walking foot evenly feeds top and bottom together, so there is none to very little stretching of one or the other.

If you are doing straight line quilting you really need to use a walking foot. You can SID using the walking foot if it is open in the front. Since (as nhweaver sais) the walking foot feeds the top and bottom evenly you have less puckering than if you use the SID foot (sometimes that foot will dig in and do some stretching).

My current machine has the accufeed (an action similar to the walking foot) so I can use a SID foot. I normally use the open toe foot since I like to see where my stitches hit. I do go really slow for SID.

I took a Craftsy class today--"Design It, Quilt It: Free-Form Techniques" taught by Cindy Needham. She's a big proponent of stitching in the ditch--she calls it ESS (if I remember correctly), Every Stinking Seam. She says that doing this anchors the blocks and stops your fabric from creeping across BUT here's the catch, she pin bastes her quilts. I don't think that you will have the creep factor if you are are spray basting. A walking foot is good if you are doing straight line stitching because it moves the top layer in tandem with the bottom layer (I don't use a walking foot when I've spray basted because my fabric doesn't move) and I think a ditch foot won't be necessary if you're careful as others have said. If I had to make a choice, I'd get the walking foot. Cindy showed samples of quilts made with and without stitching in the ditch and I have to admit ditching did make the quilt look a little better. Also ditching before you add your other quilting adds a lot of extra time to finishing your quilt--depends on how fast you need to get it done. That being said, as long as you use enough quilting throughout your quilt it won't fall apart.