Jeff set the thing up properly. Check out the pics I've attached from his other thread.
Nice tractor!
I'd be bummed also, except I DO think that for the other 90% of what it will be used for the shorter wheelbase and lighter weight will prove to be an advantage.
I think D2's suggestion is the best one. Just get a second spear for the rear and carry two bales at once. Once you get the hang of it, moving one at a time will seem pretty darn slow. I'm also guessing the turning radius might be tighter on the Kubota and that will prove an advantage over time.
If it were me, I'd be setting that thing up with a quick hitch and ballast box on the rear anyway. The additional weight on the rear will help when using the bucket anyway. With a quick hitch, swapping the ballast box for the box blade or mower when you need to will only take a minute.
If your heart is really set on the Mahindra then you might as well sell the Kubota. However, since you've already sold the Deere, and now want to sell the Kubota, perhaps expectations are not realistic? If you're moving bales that are that heavy, you REALLY should have some ballast on the rear from a safety perspective. No, filled tires are not enough. You need some weight out on the 3pt. With something that heavy out in front and no weight off the back, let's say you hit a hole, you could end up in a world of hurt VERY quickly. I say this regardless of the tractor color.
No matter the tractor, if you eventually end up with a ballast box or a second spear anyway, then your research and decision will ultimately turn out to have been the correct. Shorter and lighter will prove to more efficient in the long run and is just easier to live with all around. It also won't tear up your land like a heavier unit will so you won't be forced to be regrading all of time. It's all a trade off.
You bought a VERY nice tractor. I hope it ultimately works out for you and that you don't hate it every time you use or look at it. If you do feel that way, might as well dump it as your mind's already made up and no matter how it performs it will never be good enough.
Finally, even on the Mahindra site it shows using a second bale as ballast. I would suggest them moving them around that way is no accident. See pic. That 5010 Mahindra in the pic is a big tractor. While nice, it would be a pain in the neck to live with over time due to its size. I'd choose what you did 100x over that.
Good luck with whatever you decide,
Steve