rocinate, welcome to iRV2.com. We are glad to have you join us here and look forward to reading of your adventures and experiences. Congratulations on the Hi-Lo. They are a unique unit and do very well. What does the trailer weight fully loaded? Does the Envoy have a transmission cooler on it? I would recommend one if it does not. Steep grades may be a problem but you will definitely want to keep it out of overdrive. Good luck and keep us posted as to the other particulars.
Mike, RVIA & RVSA Certified Master RV Technician
Amy, Dr. Assistant - Roxie & Mei Ling, four legs each
2000 Gulf Stream Scenic Cruiser 450 hp & 1330# torque
06 Saturn Vue, 06 Chevy Z71 4x4 & 2014 Corvette Z51 M7