I drove my single Suffolk in a forecart that was hooked to a 4x8 flatbed trailer loaded with 2 round bales. Went approx 11 miles to deliver the hay to where my cattle are located. He went up and down hills no problem, trotted on the straightaways and trotted all the way home empty. He does a fair amount of work 3-5 days a week but I have no other experience to gauge if that is too much of a load, or if my horse is strong, middle of the road etc. Thanks.

Kristen,
I keep a close eye on breathing, sweating, and struggling under the load. Load light and go often . When possible , lighter load and make extra trips. I do the same thing ,when I bring my hay in , but I use two horses. Two rolls (2400 lb) , When you put wheels under the load it takes a lot of the work out of it. If they are not breathing heavy , then you're not over doing it.
Horses that are over weight is the biggest problem , in my opinion. I stop occasionally to check their breathing and give them a few minutes to blow.
Shanen

This question is why pulling competitions were invented. Get everyone on the same footing, pulling the same load. Comparing apples to apples.

How much did the bales weigh? Guessing your horse is in good using condition considering you don't use him every day. You treat him right instead of just playing with him.

That sounds like a job well done by a good fit horse, the kind you want. When the horse is willing, it makes the day go smoother. Smooth days are a good thing. Hold onto horses that give you that chance. Price accordingly if you sell him, eh?

Not every horse can do as well with the load you hauled, but every horse is good at turning around and jogging home. :-)