I'll be replacing my combined heater/AC unit in the next couple of weeks. I am also considering upgrading the crawl space ducting to hardwall. It is currently softwall and the entire system is roughly 25 years old. I would like to go hardwall to make sure I can 100% seal all ducting and want to put in a system that will last another 40 years! Does anybody have any feedback for advice on running hardwall versus softwall ducting in terms of performance?