Yeah, shims can be really handy; I have 3 router tables, set up so I can do raised panel doors without changing anything (one for stiles, one for rails, one for center panels) - all 3 tables have Jessem fences. I added some small micarta blocks with separate hold-down knobs.
That way, if a particular router bit is better doing several passes, I set the Jessem fence up so the cutter would take its full depth in one pass; I also lock down the micarta blocks snug against the back side of the Jessem fence - then I can loosen the Jessem and slide 1 or 2 shims between the Jessem and the micarta block.
That way, the first pass is maybe 40% of the total cut depth - remove a second shim, cut next pass; then the next-to-last pass I'll use just a thin cardboard shim - that way, the FINAL pass (no shims between micarta and fence) is more of a "burnish" than a cut - I've done complex moldings that way that felt like they were sanded with 400 grit.
I'd post a couple pics of the setup, but pretty sure that memory card is in the camera, which is 100 feet away in the shop. Let me know if interested and I'll post 'em manana... Steve