I installed the Kubota 3rd function on my LX. Took me the better part of an afternoon. Very straightforward but my tires aren’t loaded. I understand your concern but for what my dealer wanted to install it I’d still take the risk.
Plenty of good grapples to be had. I wouldn’t be too concerned about the weight. Mine is 300 pounds (Virnig 60”) and still picks up more than I need it to. I’m clearing out over 100 downed tornado trees and the only time it struggles is when what I am trying to lift is too big to safely move anyway.
I was also looking at an ammo can bolted to the loader frame for carrying a chain. Any worry about the bolts pulling through the can with the weight of the chain and bouncing around?
Nah, no worries at all. I put fender washers under the bolt heads inside the can, and it's pulled up tight against the ROPS so it can't really move (which is how things come apart). The 1" box beam bracket I made really turned out strong. Pretty sure I posted some photos of the brackets in here somewhere. I just matched the tilt angle of the ROPS with the vertical arm, and then leveled the bottom part, welded it, then ground the welds smooth. I threaded 3 short 1/4-20 bolts into the bottom tube through clearance holes along the bottom edge of the can, then through-drilled the can and bracket for the bolts that go through the existing holes in the ROPS below the hinge. I put the bolts on with aircraft (nylock) nuts to keep 'em from falling off even if the bolts get loose. It'll take longer to empty the cans than it will to tighten the bolts back up.
My tires ARE loaded, AND oversized R-14T's (because I originally intended to put a backhoe on it). As big as they are, they'd be STOOPID heavy. I don't think I can handle one of those things by myself, and finding that out when I take the last bolt out is NOT the time to come to that realization. I think I can do it by taking the seat off if I'm careful with the seat switch wiring, or maybe just yank the quick-hitch off and do it from the backside of the tractor. I've got pretty long arms, as long as there isn't too much shoulder strain involved. I certainly don't want to tear a rotator cuff (again). Twice on the right and once on the left is enough.
I'm also looking at some kits that combine the 3rd function with a couple rear remotes too, which means only one supply (PB) and one return line (T) to handle all three functions I want to add. My only gripe about them is the FEL boom mounted hoses are all rubber, not rigid. PB and T lines go to one place (no TEES or extra banjos), which means longer hoses from there back to the FEL mount for the 3rd function, but the valve body mounts on the ROPS where the Kubota remotes product does making the Remote hoses/fittings very short. That arrangement would be good for top/tilt and 3rd function. Wonder if I can get the boom-side plumbing from Kubota (I just like the idea of rigid lines) and the valve kit that I've been admiring. Good price on it for 3 valves. Hydraulics valves are bloody expensive.
I'm looking at something for picking up leaves, deadfall, and debris, nothing heavy, but a LOT of it. I don't mind multiple trips or sawing things up so the tractor can handle it. I have no intention of trying to push stumps out of the ground with it. That's why I have a sub-soiler and a stump bucket and other techniques to remove most anything up to 12 inches diameter. The one I'm admiring most at the moment is about 242 lbs. A bit light, but it's not something I'm going to buy to try to make a living with. It'll have application for a long time because I move tons of leaves every year, and a light one wrapped with chicken wire would do well for that. It is a root-rake clamshell style, but I'm not so sure I'd tackle many roots with it, certainly not some of the mower killers in my yard.