I found a work around...

The crop data is stored as json inside the Archetype so you can extract it then re-create the url using the data.

@inherits Umbraco.Web.Macros.PartialViewMacroPage
@using Archetype.Models;
@using Archetype.Extensions;
@using Newtonsoft.Json.Linq;
@{
    foreach (var itm in CurrentPage.GetPropertyValue<ArchetypeModel>("moreImages"))
    {
        string[] c = { "0", "0", "0", "0" };
        string src;

        JObject o = JObject.Parse(itm.GetValue("additionalImage"));
        // SOURCE
        src = o["src"].ToString() + "?crop=";
        // CROPS - I needed the 5th crop but you can adapt...
        if (o["crops"][5]["coordinates"] != null)
        {
            c[0] = o["crops"][5]["coordinates"]["x1"].ToString();
            c[1] = o["crops"][5]["coordinates"]["y1"].ToString();
            c[2] = o["crops"][5]["coordinates"]["x2"].ToString();
            c[3] = o["crops"][5]["coordinates"]["y2"].ToString();
        }
        for (int a = 0; a < c.Length; a++)
        {
            src = src + c[a] + ",";
        }
        src = src.TrimEnd(",") + "&cropmode=percentage&width=600&height=600";
        <img class="content-page-image" src="@src" alt="@itm.GetValue("imageTitle")"/>          
    }
}

Its not the cleanest or tidiest way of doing things, but it worked for me!

is working on a reply...