I'd agree with no. I know it's a speed game, but there's a reason safeties play 10 yards off the LOS...to give them a head start. Safeties don't need to be as fast as CBs (well, maybe a FS should be close...if you buy into the FS=big CB and SS=little LB).
However, you will HAVE to get speed, agility, and vision all to the second cap, which requires a lot of points. Also figure that tackling needs to be capped, strength should probably be close (especially if you're a special teamer) to capped, stamina needs to be high, and jumping and confidence need to be to 30. That's a lot of reqs (as compared to other positions).
I'd go to 68 and stop. But that's just me.