I bet on the Rams against the Ravens last year, the spread was under 7 I believe, and it was easy money. They didn't play a single starter, and we would have played ours into the 3rd quarter if we weren't ahead by so many points.
I was planning on doing the same thing this year, but 8.5 is a lot of ground to make up. I would NOT be betting on the Ravens though, under any circumstance. They won't play any starters again, and we should be ahead easily in the first half. I would say find the point spread for the first half, and bet the Rams for the first half bet only.