I don't know what color you used, but be very careful of sanding the clear and hitting the base. There is a thread I started about repairing base that is hit when sanding thru clear. It can make for some real headaches.
That being said, obviously I cannot see how bad the OP is, but there are safer ways to fix it. If it is real bad, you could simply scuff the clear and shoot a couple additional coats on as sacraficial material. That way you could safely sand with say 800 or 1000 to get it flat with less chance of hitting the base. You could also take 800 or 1000 and try to knock down some of the OP before shooting more clear to make it a little smoother for the next sanding session. If you use the slower activator it may actually lay out pretty good over the OP that is left.
Trying to use 400 for clear is just too risky specially over 2 coats.
Just my opinion.... then again I screw up regualrly.
Aaron