Is this legal?

[Snake~eyes]

NFHS,
Rule 7-2-3
Of the players of A who are not on their line at the snap only one may penetrate the vertical plane through the waistline of his nearest teammate who is on the line. He must have his hands in position to receive the ball if it s snapped between the snapper's legs but he is not required to recieve the snap. Any other player(s) must be in legal position as a back.

According to your description this is legal.