Been using these springs for a while, mainly cos I had a heavy pipe hanging off the back.
Not had a problem, they are a very good upgrade for the price.
It's been a while and I cant remember exactly what oil I used but I know it was a lot heavier in the rear and a bit heavier in the front.
Unless they have changed recently, you have to re-use the stock small upper rear spring because Ramtech only give you the larger spring, so you will probably not achieve a full 20% on the rear but more like 12-15%.
Also, I found the car handled a lot better with the screw tightened all the way in on each shock body.
...and they are not actually red in colour as Ramtech claim. They are more like a brass colour.