Buddy of mine ones told me, when he was driving automatic Ryder rental, truck had a problem climbing up hills in Pennsylvania.
I used to run those Ryder and Penske trucks in my old job. Most are 260hp-300hp with a real automatic allison or similar tranny. They are made to be ran around town, not really for over the road work. They are geared to give you lots of take off power but they run hard to push you down the interstate at 65. That is why they don't climb hills worth a darn.
Also, most of those engines were designed to run 300,000-500,000 miles at most. Ryder and Penske sell them mostly to places that won't be putting many miles on them a year and they can last for years. In expediting you may burn one up pretty fast. There are a lot of people on these forums that have close to a million on similar trucks, but they were built as expediters, with proper gearing and suspension and the owners have taken great care of them. I know those Ryder and Penske trucks can take a lot of abuse in their life as rentals and leases.
Just some food for thought. Are you opposed to going to a 33,000lb truck? There's quite a few in the classifieds that are real purpose built expediters.