Timing a career switch from math to TCS Short version: Is it better to switch focus as a postdoc or wait until after tenure?

Details: I'm a PhD student in math (combinatorics) graduating next year. Let's suppose that I'm a strong candidate for research-oriented, tenure-track positions in math, but my long-term research program is interdisciplinary with TCS. If I have a really productive 1-2 years of postdoc in TCS, will I have a shot at being hired in a good CS department in the US? 

I'd rather be in a CS department, but many people in my area don't share that enthusiasm (or are located in Europe). I'm worried that I'll end up with papers in both general math journals and STOC/FOCS and still be unhireable. Should I wait until after tenure? 

Edit: Here's why I'm asking. I have postdoc offers in both math and CS departments - I want to take the CS one, but all of my publications are in math journals, and the CS postdoc won't make me a stronger candidate for math departments.
My 2 cents. I would say that getting hired in the theory area in CS departments, even in good times like now, is difficult and depends on many factors. Counting on getting hired even with a productive postdoc is not a good idea. You should try but keep the expectations reasonable and be prepared to be hired in math and enjoy doing the work you like at the interface. If things work out really nicely you can try moving later in your career as well.