A few people have been scammed on the site, Only use paypal to pay for items for sale by other members. If they will not use paypal, its likely a scam NEVER SEND E-TRANSFERS OF ANY KIND.
I used Cogent Dynamics with the stock springs and oil setting, Motul 5W oil. This resulted in a 12 mm preload on the spring. No sharp jolts off square bumps and and no bottoming. I still have the stock rear but the front improvement helped out greatly.