Hebs and Shetlands are the same size, so the benefit of that cross would not be size, but to maintain the primitive character of the meat, and the sheep itself, if for some reason, you have only one breed of tup. It's years since we did that cross, and then only a few times, as we don't breed primarily for meat.
When you say 'what was the cross like', do you mean the appearance, colour, fleece, meat quality, hardiness, or other specific traits, or just was it a worthwhile cross ?