Hey jon,
Well i just had to cross a similar bridge. I poured a conventional 8" thick foundation wall. We formed it up to match the exact footprint of my house. What i should have done is set the forms 1" wider ( if the foot print is 24' by 36', make it 24'1" by 36'1")all the way around. So in turn you would have a 1" lip of foundation wall to rest the panels on, which is plenty strong. Those panels don't way that much and after nailing them to the frame every 6" to 8" inches there isn't that much of a load bearing on that lip .
That is what i should have done looking back on it, but what i did to remeady the problem is set the p.t. sill plate over the edge of the foundation 1". So i would have a lip to rest the panel on. It doesn't have to be wide enogh to support the whole panel. Just enough to give you some relief and those ring shank nail are TUFF (or you mentioned screws). After the panels are attached to the frame they should move anywhere. That is just my two cents. I am building my frame up here in Randolph if you ever want to come up and take a look. take care Zac
