Here's a quick way to adapt the Panels CarouselArranger to peek the previous panel.  By setting peekWidth on the Panels instance, this modified arranger will offset the left by that amount.  It isn't a perfect implementation (e.g. you can see the prior panel in the background when you slide the current panel away) but it would probably work in many cases.

For simplicity, the kind inherits from CarouselArranger.  I've only modified the arrangeNoWrap method so the contents are virtually copied verbatim.  Look for peek to find the customizations.

enyo.kind({

    name: "extras.CarouselArranger",

    kind: "enyo.CarouselArranger",

    arrangeNoWrap: function(inC, inName) {

        var peek = this.container.peekWidth || 0;

        var c$ = this.container.children;

        var s = this.container.clamp(inName);

        var nw = this.containerBounds.width;

        // do we have enough content to fill the width?

        for (var i=s, cw=0, c; c=c$[i]; i++) {

            cw += c.width + c.marginWidth;

            if (cw > nw) {

                break;

            }

        }

        // if content width is less than needed, adjust starting point index and offset

        var n = nw - cw;

        var o = 0;

        if (n > 0) {

            var s1 = s;

            for (var i=s-1, aw=0, c; c=c$[i]; i--) {

                aw += c.width + c.marginWidth;

                if (n - aw <= 0) {

                    o = (n - aw);

                    s = i;

                    break;

                }

            }

        }

        // arrange starting from needed index with detected offset so we fill space

        for (var i=0, e=this.containerPadding.left + o + peek, w, c; c=c$[i]; i++) {

            w = c.width + c.marginWidth;

            if (i === s-1) {

                this.arrangeControl(c, {left: -w+peek});

            } else if (i < s) {

                this.arrangeControl(c, {left: -w});

            } else {

                this.arrangeControl(c, {left: Math.floor(e)});

                e += w;

            }

        }

    }

});