dssur
+1y
are the cups too short? That would make the bag not squish all the way at full drop, and keep it from lifting...
What I mean is, an RS6 should squish to 3 inches tall, and then will lift about 7 inches. With the geometry of the front end that should give you about 10 inches of lift. If the cups are too short though, the frame will bottom out before the bag does, say at 6.5 inches. So you limit the lift to about 3 inches, with geometry about 4.5 inches.
Are you using enough pressure? If the front end weighs a ton with a big V8 and all that heavy steel you'll need at least 150 psi to get up.