Code tested by William:

This is the change to the diagonal overlay code. Just add a:

.skewed-overlay::before {

background: 0 0;
background: -moz-linear-gradient(-155deg,transparent 15%,rgba(255,255,255,.2) 15%,#fff 45%,rgba(255,255,255,.85) 45%,rgba(255,255,255,.3) 80%,rgba(255,255,255,.9) 80%,rgba(255,255,255,.9) 90%,rgba(255,255,255,.95) 90%);
background: -webkit-linear-gradient(-155deg,transparent 15%,rgba(255,255,255,.2) 15%,#fff 45%,rgba(255,255,255,.85) 45%,rgba(255,255,255,.3) 80%,rgba(255,255,255,.9) 80%,rgba(255,255,255,.9) 90%,rgba(255,255,255,.95) 90%);
background: linear-gradient(-245deg,transparent 15%,rgba(255,255,255,.2) 15%,#fff 45%,rgba(255,255,255,.85) 45%,rgba(255,255,255,.3) 80%,rgba(255,255,255,.9) 80%,rgba(255,255,255,.9) 90%,rgba(255,255,255,.95) 90%);

}

On second line from the bottom. It's -245deg