I recently looked into the tandem brake dilemna myself. The results are not pretty. I upgraded our tandem from really cheap v-brakes to Avid Single Digit 7s. They are better...but not even close to my Shimano Ultegras on my single. There seems to be a big unfulfilled market for nice tandem brakes. I have not found a solution that I thought was decent. You're right, you probably don't need a drum brake. I have disks on my mountain bike and I love them. If your frame has the braze-on tabs, go for it. You'd think someone would come up with a good brake solution for tandems.