I've done several searches without any luck. Does anyone know the grade percentages of the hills on the SCT, specifically the section between the connector crossover bridge to Hicks Road and Mount Thrashmore?

Do a quick search on railway maximum grades....I want to say it's like 4%, but cannot recall for sure. It's based in an old rail bed, so the trail doesn't climb any more than a train could.

I am not familiar with those roads.
The Trail typically has gradients of 2% or less, I believe,but some are quite long.
This applies for the Trail in general EXCEPT....in some places between Rockmart and Cedartown,
where the Trail exits the RR bed and has to traverse local roads for a bit. From what
I have been told, there are some significant HILLS on that stretch.
Plus, going east past the 0 mile marker at Mavell Road, there is a pretty steep rise coming up to the shopping center on the East-West Connector. It is a DOOZY....but, short.

You might have luck with a Strava Segment search.

https://www.strava.com/segments/explore

Visually, you can see this on google map. Put checkmark on Terrain and Bicycle.

Thanks for the replies and yes, that hill east from the Mavell Road Parking lot to the Connector is a pretty good pull.