Can you give us a model number on the Icon piston? That '6 thou out of the hole' number does not make sense so we can research it for you if we get a PN. Tnx.
The same goes for the springs PN; can you give us the Hughes PN on the valve springs? Telling us that they came from Hughes does not really tell anyone anything.
As above.... 'being done' at 5400 RPM is not making sense with this cam spec of 232 @ .050". PRH is IMHO saying one half : the top end RPM range is being cut off by the springs not being good enough to stay stable. This is a higher RPM cam.. not the highest range cam by any means but not 1500-5400. Do you have a Hughes PN for the cam?
And YR is going at the other possible half of the problem: This is not a small cam, and the low end RPM's are not going to start at 1500..... closer to 2800-ish IMHO. If you engage the clutch at an RPM range below that, then the engine is going to be sluggish/boggy until it gets revved up. The manual trans is unforgiving of a poor low RPM setup.
Several folks are really trying to help you, but something is not hanging together, and PN info will help.