2012 GMC Sierra / Size of TT?? (NEWBIE)

That truck is really going to struggle with 9600lb tagging along regardless of what the manual says. The 5.3 and 3.42 gears say fuel economy, not pulling power. If momma wants a larger trailer go for it by all means, not all of us have that luxury, but do consider a truck that is more suitable. The 5.3 might work with lower gearing but a 6.0 would be better. You can't have too much tow vehicle but you certainly can have too little.
Our first trailer was within the published rating for our then truck but the initial trip told us otherwise.