The alu F16 masts do have some margin there. You can remove some weight and not violate the tipweight ruling. You certainly won't violate it by removing the halyard block and halyard.

Carbon mast are at the minimum tipweight and must be careful not to go under it. We set the tip weight somewhere between the two extremes to improve equality but still allow some development. So you could build carbon masts lighter and the alu mast could loose some more tipweight (lighter spreaders, dyform wires etc).

Wouter