Negative Shim:



I wouldn't do this to just any stem however. Only where there is a lot of meat around the clamp.
Any metal removal here must have a uniform and self-centering component to the cutting action along the interior of the clamp, which this method achieves. The clamping tension on the exact-sized sanding mandrel is key to the self-aligning and uniform cut (notice the Allen key adjusting the cutting force by very slightly spreading the clamp)

And those French stems also sure weren't designed for use with wide bars, seems they were never paired with wide bars in those days! Some of the "death stems" are as flexy as can be to begin with.

As counter-intuitive as this seems, I have not experienced any hand numbness since moving my saddle position forward on all of my bikes!
I attribute this to the albeit more-aggressive riding position making it quick and effortless to transition to the out-of-saddle position, instead of having to do more of a big heave off of the saddle. Moving around more freely, I thus stay loose on the bike, with no tendency to allow my arms/hands/shoulders to stagnate in one fixed position. As well, the forward positioning encourages a more vigorous pedaling effort, which must be taking weight off of my hands. Further, a more-forward saddle together with commensurate stem-extension increase reduces the bend angle at the waist, which promotes circulation through the body. So hopefully your frame is on the large side, large enough to promote this more stretched out (and straightened out) positioning, while allowing the most comfortable reach to the bars and promoting effortless changes of position in response to the grade of the road.

Whether a Noodle handlebar will improve circulation to your hands will depend on what hand position you are using, but setting up the bike to allow comfortable use of both the tops and the drops might even better promote circulation through the arms.