Joe;
Nice little forge. I've been waiting for a callback on one like that myself.
The one I built for traveling has the same problem as a regular rivet forge, that is high sides, and no firepot. Main problems are only being able to heat the "point" of a piece unless you bend it to get it into the fire, and keeping your fire "corralled". Hard to work in a little pile of coke, but it's also hard to keep your fire from spreading to the rest of your coal.
I got around these problems by using a bearing race, aprox 8" dia, 1 1/2" high over the grate. This allows me a deeper fire because I can continually pull coke up on top, brings the heart of the fire up to the level of the rim of my forge pan, and blocks the fire from creeping out into my reserve fuel supply. The heat transferred also allows the green coal to slowly coke, ready to be broken up and pulled up into the fire.
I used the race because that was what I'd found at the scrapyard. You can use a section of heavy wall pipe, an old el cheapo cast iron saucepan with the bottom cut out, etc., just anything to raise the level of your fire to the point that you can work in it about horizontal.