Hi, JamesonF. I too am from Wisconsin and planted some peppers back in January. In fact I just posted a similar question regarding one of my Ghost Pepper plants. I was wondering how long I can keep it in its current pot before something more roomy would be needed since it can't go to it's permanent home outside for another 8 or 9 weeks. I know depth is a concern since some containers do not drain real well and the standing water in the bottom will cause all kinds of problems. If it is a good draining pot with good draining soil, I would go with something about 6 inches or so deep and close to that wide. Many times when transplanting starters, I find they are rooted all the way out to the sides and it is safe to assume they would enjoy more room that way too. When i have to put my seedlings into the next sized temp pot, I am thinking I will go with something 5-6" wide and about as deep. I dont want to have to do another temp transplant before it finally warms up enough up here. Hope this helps but I am by no means a master gardener and last year was the first year I even grew hot peppers (Cayennes and Habs). This year I have several varieties but my Bhut Jolokia's (Ghost Peppers) are my pride and joy right now. Check my photo in the post just after yours.
PS: The snow should be gone in a week if you go by what the weather reports are saying...yippeeeee.

Well isn't great to meet another Bhut enthusiast, especially a Wisconsinite one! I have a few questions for you that I'll post on your post.