Hopefully this will be of interest to a few of you & at the same time earn a little bit extra for the DDK 10K for 10 years Charity Pot
Just to note, I have no affiliation with the company. I'm a very happy customer
Not sure if anyone has heard about CG-locks ? I hadn't until I started searching for something to help with some lower back pain I've been having recently. It was then I heard on other Porche forums about the CG-Locks
In addition to claiming to help with seat posture, it has the benefit of holding you in place when 'performance' driving 
http://www.cg-lock.co.uk/
http://www.cg-lock.co.uk/cg-lock/
http://www.cg-lock.co.uk/app/performance/
http://www.cg-lock.co.uk/app/medical/
I bought one last week & have been really impressed. It allows you to adjust the lap belt portion & keep it locked in that position .. bit like harnesses , but allowing the remainder of the seat belt to act normally. So far I am feeling a lot more 'fixed' in my seat and can already feel I keeping my seating posture as opposed to slipping down in the seat & curving my spine .
fitting is straight forward, requiring you to clamp the device to your seat belt tongue.
Anyway, the purpose of this thread
..... a few emails later & I have organised a DDK group buy , which means we can buy them for £34.99 instead of the usual £49.99. To get the DDK group buy discount, on the order page enter the following code into the discount box :
DDK
( easy one to remember
)