If you're near Fort Collins I'd be happy to take a look and give you my $.02
Flagstone is a lot more forgiving. You can lay it a little uneven and call it rustic, or cottage style, if you are ok with that end product. However I wouldn't recommend this if anyone who is unstable on their feet...
I think you would be fine pulling the bigger trailer in dry conditions. You might need to adjust the weight distribution of your load in your truck/trailer to not have too much tongue weight/cargo weight in the truck. And, if the trailer brakes are functioning properly, they'll help stop you...