Wow seriously old thread. Either way the question was never definitively answered. I have been wondering about this for the last 20 minutes after finally deciding that I'm not a fan of the way the cup holders are designed in respects to the individual size of each holder.
After searching on google and CL and LOC, I haven't found out the answer. I'm a bit hesitant to just buy the part and hope it can be done. Brand new the part is ~$140. Not my particular price range, but would look into getting a junkyard/salvage part. I know a dremel would do the job all the same but the ls430 has those little flex arms. That in conjunction with a lovely set of wood trim for the ls430 cupholders (I recently found on JPY) has me kind of set on finding out if this can be done.