Maybe it's about right as it is. I like SF/under (27-20), but I'm horribly biased. Going to try hard not to sound like a fan these next two weeks.
Look for props involving going for it more often on 4th down. Jim Harbaugh is going to have trouble sticking with Akers when it's a close call. Also, for in-game betting, there is some strategy around waiting for the team to kick the field goal when they "should go for it." In other words, the line moves against the team when they kick the chip shot. Should Jim Harbaugh decide to go for it in this spot, the line behavior will be different.
Not 30 years ago, when the Redskins beat the 49ers in the NFC Championship game, the Washington kicker had missed FOUR field goals before lining him up to kick the winner, which he did of course. Amazing what a different time we live in.