I'm afraid I have to respectfully disagree with your suggestion to use stiffer antisway bars (e.g., IPD's) in an off-road (i.e., any irregular road surface) application. Allow me to explain.

Swaybars (actually, they're "anti-sway bars"), while obviously reducing sway (technically, a "rolling" motion), increasingly link the right and left sides to lessen their "independence" -- i.e., their ability to respond individually, and move oppositely, to irregularities in the road surface.

A swaybar resists one wheel moving up and the other wheel moving down, which is what happens when a car rolls to one side. Thus, a sway bar should have no affect on a "bump" that is across the road (e.g., a "speedbump" or a "sleeping policeman" as it's called in various parts of the country) because in that case both wheels move up and down together. However, when one wheel hits a bump or a dip that the other wheel doesn't encounter, it's the same effect as if the car is rolling over (one wheel goes up or down relative to the other), and this is resisted by the swaybar.

On irregular roads, you want the *least* swaybar stiffness. In fact, the well-known reputation of Land-Rovers (even without locking or limited slip diffs) stems mostly from their unsurpassed "articulation" -- i.e., their ability of their individual wheels to fully extend and retract, following irregularities of the "road" (or trail), independent of the other wheels, to maintain traction by keeping the tire tread pressed against the ground. Other reknowned off-road vehicles such as my own original-series (W460 chassis) Mercedes-Benz Gelaendewagen must rely on locking differentials to match a Land Rover Defender without same!

Even if you have no traction concerns -- i.e., you're not really off-roading, but just, e.g., going to your hideaway country place down an unimproved dirt and potholed road -- you probably want to enhance the independence of the wheels, not lessen their independence for that road. Stiff sway bars will increase the jarring, bumpy ride that you probably won't appreciate -- the car will rock and buck more! Cross-country rally cars, for example, and especially if there are no paved sections, are often set up with minimal sway bars (or adjustable ones), to minimize the severity of the ride, as well as the aforementioned enhanced traction.

Admittedly, a stiff sway bar might actually lessen the severity to the suspension of a single wheel falling into a pothole (because the swaybar will counter the extension force of the spring), but on the other hand, it will work with the spring to further resist the rising of the wheel if it hits a rock or tree root, as if you had stiffer springs, and increasing the jarring in encountering these. So the net advantage is probably zero if you're encountering a combination of both "hole" and "root/rock" road hazards.

Stiffer sway bars are largely an advantage on paved roads, where they enhance handling -- and IPD makes very good (very stiff) bars, while knowing how to keep the front/rear balance (understeer/oversteer) that the vehicle should have for safety. Overall, they will not help you offroad, and if you get them for on-road handling improvement, at least be aware of their disadvantage off-road.

Regards