::squee! - rubs hand together:: - one of my favourite topics
Yes, I've done it.
It's a terrible idea, especially in the rear of a coil sierra.
You've slightly misrepresented the effect - it doesn't increase travel - in the rear of a coil sierra, travel is limited by the shock length. What happens is roll stiffness drops to (almost) nothing. Roll stiffness needs to be reasonably matched front to rear. Additionally, in order for the suspension to work when the car is climbing, it's advisable to have slightly higher rear roll stiffness than front.
What you'll find is with a bolt removed, on flat ground the car will follow the nose - the front will flex after the rear has reached the limits of its travel. When climbing, this results in the car flopping over and lifting front wheels. It'll do it on even very mild climbs, and as you've noticed, is accentuated by torque.
Here's a visual demonstration, on my car. It ran Range Rover front radius arms in the rear and leaf front at this point a gazillion years ago, but the general arrangement is pretty similar to an SJ80. It had much longer shocks though so the effects are exaggerated.
Bolts all in. Note how hard the front tyre is tucked into the guard and the angle the body is on.
Bolt pulled. Note the front axle is barely flexing and the body is now on a huge angle.
there's another effect that's not immediately evident - instead of the axle rolling on the median between the two radius arms, it now rolls with the arm that has both bolts in. That can lead to some dramatic driveshaft angles.
Both bolts in
one bolt pulled
Because of the radius arm design, with a bolt removed, all the torque will be directed through one arm only. This tends to make the side with both bolts in jack up, whilst the other side with the missing bolt stays at normal ride height. Again, on a climb this is accentuated as the weight transfers rearwards, and the car will take on some very strange side angles.
I'll add with some SJ80 specific tech - pulling a bolt puts big loads on the radius arm bracket on the side with both bolts in place, and they're already too weak.
If you want to experiment with this further, put the rear bolts back in but pull the passenger front bolt in the front. Freeing the front up will transform the feel of the car off road, especially when climbing - the body will stay much more level and the car will feel much more balanced. You will notice some increased brake dive and some weird characteristics at speed, but it'll feel nice in the bush. Pulling a front radius arm bolt is a fairly common Range Rover practice, as, due to their suspension design, the rear has very low roll stiffness and the front has relatively high roll stiffness. This is done to promote road handling by making the car understeer gently and reducing body roll, but off road it's unhelpful.
Every car will get to the point where the front wheels will lift and the front will "unflex" and "push off" if it's on enough of an angle - its just a result of the front getting progressively lighter as the angle gets bigger. The idea is to try and move the angle this happens high enough that you don't encounter it under normal driving. Removing a rear bolt moves this angle closer to flat, removing a front bolt moves this angle higher.
Here's some ancient photos of my Gwagen for reference of working within and outside this angle. as I discuss below, the Gwagen is radius arm front and rear like the SJ80 but has matched roll stiffness, not lower rear roll stiffness like the SJ80.
Front flexing hard even with the car on a big climb
Woah - front unloaded due to the huge compound angle. (This is about 40˚ climb and a huge side angle. This was a very, very scary hill, long closed)
Here's some context:
Suzuki fell into the same trap as all the japanese manufacturers - they copied the British (land rover) and Germans (Gwagen) when they designed their coil suspensions but missed the point on roll stiffness. Both the Range Rover and Gwagen have parallel chassis rails that allow the rear coils to be placed outside the chassis (like the front of your SJ80) and that which allows the springs to add rear roll stiffness and helps to balance front to rear roll stiffness. The Gwagen is radius arm front and rear like the SJ80, but the parallel chassis and outboard rear springs matches front and rear roll stiffness well. Mercedes then added a very stiff front swaybar to make the car understeer. with that removed the Gwagen handles excellently and is very balanced off road. The Range Rover has inherently very low inherent rear roll stiffness with a three link A-frame arrangement, but outboard springs in the rear that introduce some roll stiffness. Whilst the radius arm front has inherent roll stiffness, the Range Rover wasn't designed to run a front antisway bar and one was only added because of ignorant drivers.
The japanese saw these coil designs but didn't want to build a clean sheet design - mostly they wanted to add coils to their exiting leaf sprung chassis. to do this they generally added radius arms in the front and a 5 link or radius arms in the rear because they're easy to package, but they missed the memo to run parallel chassis rails and outboard rear springs, so the end result was very little added roll stiffness added via the springs, because they're closer to the centreline of the vehicle - so basically, the worst possible combination. and that's why every bogan reverses their GQ patrol up obstacles to take photos with the front flexing.