Honored Contributor
Honored Contributor"Preserve Fan-out Free Register Node" should be all you need (no need to route the signal to the top level) if you are using a device family supported by this assignment.
From QII 7.2 on-line help: --- Quote Start --- Preserve Fan-out Free Register Node logic option -------------------------------------------------------------------------------- This option can be set in the Assignment Editor. A logic option that specifies that the register should be preserved in the design even when it becomes fan-out free. This option is available for supported device (Arria GX, Cyclone II, Cyclone III, HardCopy II, MAX II, Stratix II, and Stratix III) families. --- Quote End ---