I took the passenger seat out yesterday and removed the top leather and started adding black foam to the existing seat foam. Tonight I will start forming the upper seat to give me back and lumbar support and just have to keep it within the factory seat leathers. I did this on my old gt500 seats and it made a huge difference. I spray glue to both pieces and let drive over night and then will mold with eletric knife and use my battery powered angle grinder with a tiger wheel on it to smooth it down. I will take some pics of it as working the shape. The leathers are very simple to get off and when putting back together instead of hog rings I will use zip ties they get the leather alot tighter

 

I know you've already planned out your mission, but here is tidbit for anyone else thinking the same thing (you had to buy the Portfolio edition to get adjustable lumbar support so there's probably tons of base models out there without). There are aftermarket lumbar support systems one could install, easily searchable on the web. Actually they are pretty cool, a rubber bladder is fitted underneath the seat cover, a vacuum line run out the bottom inside where a sphygmomanometer bulb (like from a blood pressure thingamajig) is attached and the user can pump it up to his/her liking. Many upholsterers will even make a matching cover for the bulb. If you really want a cool one, find a mid-80s Toyota Supra or Celica GTS in a salvage yard with a toasted driver seat and cut the lumbar bladder system out of it. It has three separate chambers that can be aired up individually to change not only how much lumbar support, but also the shape or how high or low you want it on your spine. Those cars were really popular to steal back in the day for their incredible seats. I've seen those seats in everything from hot rods to Jeeps.

 

A 2011 Supercharged didn't come with adjustable lumbar support??

Both my 2011 XF Premiums came with it, so I am surprised that a more expensive XF model of the same year wouldn't have that feature.