In the end, I did rent the car carrier. Fortunately, Penske allowed me the flexibility to pick up the truck first, load it, and then pick up the trailer a few days later. (They allowed the same on the return: I dropped the trailer first and then unloaded the truck.)

I had another thread about parking the truck, and I have an update on that here:
https://www.aaroads.com/forum/index.php?topic=19794.msg2216705#msg2216705We were running behind on packing and loading the truck, and rather than departing rested and ready at noon on Friday, I was instead sleep deprived and sore, having been awake and loading for the previous 36 hours straight. I finally hit the road at about 7 p.m. Since I was so tired, I didn’t get far, and I stopped in Wildwood, FL for the night.
I took the truck through a CAT Scale (out of curiosity) and found it to be much more heavily loaded than I anticipated. Total weight was over 25,000 lbs.—about 850 lbs. from exceeding the truck’s GVWR and landing in CDL territory.

After a sound sleep, I continued along the typical route (US 301, I-10, I-295) under low traffic and ideal conditions. Not long after I got onto I-95, though, traffic was an on-again, off-again crawl from Jacksonville well into South Carolina. Based on the extraordinarily heavy volume of rental trucks, trailers, RVs, and northern plates traveling the same direction, it would have appeared to be the snowbirds’ official day to head home.
I exited onto I-26 and then I-77 as I had originally been considering, and traffic was essentially a non-issue from that point forward. But with all of the stop-and-go on I-95, plus my 55 MPH top speed with the trailer, I didn’t make great time. I stopped Saturday night north of Charlotte.
That allowed me to hit the hills of the Piedmont and Blue Ridge on Sunday morning while I was wide awake and had the benefit of daylight. For the most part, the truck was able to maintain at least 45 MPH on even steep grades, although for a few brief moments, my speed dipped as low as about 40. There were generally other heavy trucks going about the same speed, so I wasn’t the lone obstacle.
I did encounter some truck trouble, however. Many diesel engines use diesel exhaust fluid (DEF) to control certain pollutants in the exhaust, but Navistar (International) decided to use an alternative setup where the pollutants are caught in a filer and then burned off by exhaust heat. These Navistar engines have been the source of numerous customer lawsuits. In short, I had trouble with the emissions system; the engine sometimes ran roughly, lost power, refused to start, and in some cases, stalled.
The scariest moment occurred that night in Carlisle. I had just refueled at the Petro and was waiting for the light to turn green so I could pull out onto US 11 and enter the PA Turnpike. When the light changed and I stepped onto the accelerator, the truck slowly crept out into the intersection before the engine shuddered and died—with the truck blocking both directions of traffic. I frantically turned the key—the engine cranked and cranked but wouldn’t start. Meanwhile, the light had changed again and tractor trailers lined up on both sides with truckers angrily blowing their air horns. (Aside: To do what? Clearly I’ve stalled out; it’s not as if I’ve absent mindedly gone into a daze and will snap to attention at their honking.)
While dialing emergency road service with one hand, I kept turning the key with the other, and finally, the engine sputtered to a rough idle. I managed to coax the truck onto the right shoulder and eventually built up a bit of speed: 5...10...20.... By the time I neared the Turnpike on-ramp, I was going about 35, so I thought I’d take my chances and continue toward Philadelphia. I did make it—at about midnight Sunday night.
I plan to write a letter to Penske about the truck trouble. The return location was actually a Hertz rental counter, and unfortunately the staff knew nothing about trucks and didn’t seem to have any authority to act. Ironically, I was absolutely insistent about renting with Penske specifically to avoid the decrepit, unreliable equipment in U-Haul’s fleet. In fairness, though, the customer service was generally excellent and I’m inclined to accept this as an isolated problem. The truck I received was an 2012 International Durastar with about 150,000 miles, and I think this truck would have to be among the oldest in Penske’s fleet. Hopefully this isn’t a sign that Penske is no longer the gold standard of truck rental they historically have been.