I've had good luck with those medium sized barrels, so probably no need to change it out unless you do a rebuild. If you can do a little build up where the riser sits and get some more riser height overall, from burn floor to riser top, you'll help the stove out a lot. You'll have to bring up the barrel as well, but I've had good luck just adding a cob ring to build height for the barrel base. If you can get 6"+ more riser height it will help a ton.
Your a bit thin on riser insulation as well, but it most likely wont affect performance unless you are doing real long burn sessions. Keep your eyes open for a small barrel, sometimes called a "grease drum" and pretty easy to find at big truck oil service shops. They make perfect insulation canisters for the riser. I've used them in the medium barrel like you have there and although its kinda tight it works well.
Awesome hoop house man. I've been an Eliot Coleman fan for a while now, but haven't implemented anything as in my climate I've got greens all year even outdoors with total neglect. Someday though. You're kinda giving me the bug right now.