If you are willing to put a firm cap on the size of your next trailer then you may be fine. Then again, what are the chances you will walk in and find a trailer that comes in a little bigger than you thought?
For what it is worth I run with the max payload and with the crew cab and canopy the truck scales at a little over 6,000 before loading up for a trip. My TT loaded is 8,100 lbs and the truck has done very well. My TT length is 28', so shorter than what you are describing. It has proven to be a very stable towing platform and I really appreciate the mpg running empty, particularly on the highway. As for the 5.0 it is going to be revving more by design and has less torque. I happen to like the lower rpms, this is the quietest rig running down the highway I have ever had.
Not sure how you would feel with the extra few feet of length. If you expect to tow in cross winds with a TT over 30 feet I would be looking at the heavier F250. Also, if I am not mistaken the receiver is rated for 1150 so depending on what % you have on the tongue it may get a little close.
SkipNChar tows 34' and has been happy with his outfit (SuperCab / Max Payload / EcoBoost).
Good luck to you,
Stu