As far as the IRS,yes this is typical...you need the regular solid rear axle for heavy weighted towing and towing long distances...so for comfort the IRS is awesome,but not for towing!
IM going to disagree about IRS ,once the truck is set up right
front has equal spring compresion front to rear the truck should preform great
meaning proper weight transfer.
If you think you need help go to an RV dealer and have them set it up