Attaching the foam was relatively easy and took about an hour of work. The procedure was as follows
1. Cut foam to width of 8" to fit inside the wall form.
2. Drill holes in the foam at a semi-regular spacing
3. Snap a vertical chalk line on the exterior of the house foundation that represents the outside edge of the foam.
4. Place the foam on the foundation and use a drill bit to mark the positions that need to be drilled.
5. Drill, Drill, Drill....and Drill some 11 more times!
6. Blow out the holes so the epoxy will adhere to the inside.
7. Test rebar for fit.
8. Fill holes about 3/4 full of epoxy.
9. Insert Rebar slowly, squeezing epoxy out of the hole. Scrape off the excess.
10. Apply a good amount of foam compatible glue to the back of the foam.
11. Fit rebar through he holes in the foam and push the foam tight agains the foundation while squeezing out the glue.
12. Complete the same procedure for the other foundation connection.
13. Continue forming the garage/porch foundation.
Will it be worth it? Without modelling its hard to tell but given that it was such a low cost ($70 + 1 hour labour) it made sense to do it.