In the shipment with the SL plug Raderwerk sent their latest light weight seat. I weighs in at a "heavy" 399 g. Not yet sure if I am comfortable going this light but it is an impressive bit of composite laminating. To put this in perspective the Ventist seat pad is lots heavier.
The Ventist seat weighs in at 476 grams. This is the thin version of the pad. The comfort one will be about 1/3 more.
In the SL I will have to ditch the pad as it takes up too much space, it move me forward a couple of cm. Given the choice between fitting and the pad I'll take the fit and deal with the comfort issue with some padding only where required. More work but less weight.