As to the OP's question? No I'm not. I'm sure that DW/me will be paying taxes on 100% of our SS (currently would be at 85%, at our income level), that extra 15% on just a portion of our retirement income would not be enough to worry about (as Gumby has shown).
I don't want to derail the initial question, but I read an interesting article yesterday, and it applies to all those that don't plan for SS due to their age, which seems to be a lot on this thread.
Why Social Security taxes are a good deal Jeff Reeves - MarketWatch