I know you're looking for a different answer.   But I did use wildcat power for each of these challenges.   If the safety came up to the line i always ran underneath (to the inside)  him without sprinting.  I didn't sprint until i past the initial wave.  You may need to do a spin move to get by a person or two as they cut you off on your way to the end zone.

Also, if it you're not getting enough yards in one direction, flip it and try the other.  I'm always better going to the left.

Good luck with the challenges.