I think you have to go 2 5/16 on a 14k trailer, no?? If there is an option, go bigger for sure. I'm not sure about a stabilizer style hitch on a flatdeck. My brother in law has one on his 30' RV and thinks it's the cat's *****. It's pain to hook up, but whatever......
I have a PJ 20' + 5' dovetail GN with 2x 7k axles. The trailer itself weighs about 5200lbs, and because it's a goose ~ 20% of the load is transferred to the truck vs. something like 5% on a bumper-pull. That makes the useful payload of mine ~ 11K lbs. It's a deckover vs. Darin's lowboy, which I think is nicer for hay, etc. It's ~100" wide. I think I paid 5200$ US for it. I do wish I had gotten a tandem dually trailer just to max out the trucks capacity for hay hauling etc, but it more that does the job right now. I'll put 10 round bales on it, max. I wouldn't get a tri-axle style. I pulled one a while back and found it didn't handle as well as the tandem, and was not as easy to back up (the tires flex a lot when you turn sharp). It was my first GN and I must say it handles WAY better than a bumper pull. The GN doesn't seem to 'push' you around as much, and doesn't 'bob'. My friends and Father-in-Law made fun of me for 'overkill' when I got it a year ago, and they've now all conceded that "it sure pulls nice", or "it sure is handy to have around!!" Next time it'll be a 25' + 5' dovetail with flipdown ramps, a toolbox, tandem dually, 2x12K axles, electric jacks (ya, I'm lazy....), and a "deck-over-neck" platform for added cargo space. I'm pretty happy with the quality of my PJ.
I think you'll be fine as long as the bumper pull you get has GOOD brakes. Make sure you get 4 good chains and boomers before you pick up your new toy!!! Length might be a bit of an issue for you too. My 4720 with FEL and Bush Hog took up almost all of my GN.
Don't get a pintle, those are for dump trucks!!! The ball is much more universal, and lockable as you mentioned. GN hitches are lockable too.
If you do go with a GN, have a look at the B&W turnover ball hitch. I've been running one now for over a year and love it. It leaves the bed of your truck totally normal when you're not using it, and there's an option for something called a companion hitch, which is a 5th wheel if you ever need it.
Sorry for the long winded message, I love to talk about my toys!!! Hope this helps you out.
-J.