You're going to tow about a 1,000# more than I do, (my rig is at 16,050#), with pin weight of 3300...I have the dually in my sig with the 4:10 and it's my daily driver, but I tow in the mountains and enjoy the stability of the dually on some of the very curvy, mountainous secondary routes I'm on at times.
I've towed with both short bed and long bed, and with heavier longer 5er's, I prefer the long bed..
If your 5er has the indents in the front end cap, a short bed should work, think you said you had never had a problem before...shouldn't have one now
On Edit: If you've done all the math with weights, then seems like you're ok:)