I'm dealing with the same issue. I haven't quite figured out if this is going to work or not, but I bought a front (horizontally flat) bike rack in the hopes that I can move my rear rack trunk bag to the front ... and then use my (now open) rear rack to carry my tent, sleeping bag and sleeping pad on top of (with panniers hanging on the rear rack sides). The rear trunk bag is long and narrow. The idea is for the rear bag to fit between the handlebars (extending out over the wheel) thereby keeping my interrupter levers open for my hands to use without any interference. I took it for a test run yesterday, and found that I need to add some sort of a strap to the very end to help stabilize it better.

This is the trunk bag I'm talking about:
http://www.amazon.com/Sunlite-Toploa.../dp/B0013498NM

(As you can see, it's kind of longish. Rather than buy all new gear, I'm trying to make use of gear I already have).

Hope this helps you somehow.