Thank you for answering my post. Last year I had the Original Mattress Factory make me a custom mattress. It's comfortable and fits perfectly. I like the idea of the topper, but, I will have to determine if I can store it since it won't fit under the cabinets.
in case you still haven't decided what to do, my DW purchased a 4" memory foam for our Lexington and it does make a difference sleeping (love it). I would highly recommend the 4" topper. good luck.