This is long enough for a couple of posts... so lemme speak to range of motion, bumpstops, and front IFS first.

On other Isuzus (with long or short A-arms), I've seen the 'bounce' happen when the truck is lifted to an extreme.

Here's the truck's approximate rideheight stock:
[color:"blue"]*bumpstop*-------------------------[color:"red"]*rideheight*[/color]-------------------------*bumpstop*[/color]
So actual travel looks something like this:
[color:"blue"]*bumpstop*------[color:"orange"]*travel*travel*travel*travel*travel*travel*travel*[/color]------*bumpstop*[/color]
Note that in factory configuration, you will hardly EVER hit the bumpstops, unless you overload the vehicle or jump it.

...and here's what it looks like with a little lift:
[color:"blue"]*bumpstop*------------------[color:"red"]*rideheight*[/color]--------------------------------*bumpstop*[/color]
So actual travel looks something like this:
[color:"blue"]*bumpstop[color:"orange"]*travel*travel*travel*travel*travel*travel*travel*[/color]-------------*bumpstop*[/color]
In this case, at the extremes of travel, you'll find yourself up against the lower bumpstops.

Now roll in a LOT of lift:
[color:"blue"]*bumpstop*--------[color:"red"]*rideheight*[/color]------------------------------------------*bumpstop*[/color]
So actual travel looks something like this:
[color:"blue"]*bumpstop[color:"orange"]*travel**travel**travel**travel**travel*[/color]-----------------------*bumpstop*[/color]
With a lot of lift, you're pretty close to the bumpstops at normal ride height, and you'll feel them over mid-sized bumps. You'll have reduced range of travel (only 5 'travel's as opposed to 7 'travel's above) since you're hitting those stops... and coming off speed bumps and such, your wheels may occasionally lose contract with the ground, since ths suspension is stopped by the bumpstops.

Here's what TOO MUCH lift looks like:
[color:"blue"]*bumpstop*[color:"red"]*rideheight*[/color]--------------------------------------------------*bumpstop*[/color]
So actual travel looks something like this:
[color:"blue"]*bumpstop[color:"orange"]*travel**travel**travel**travel*[/color]-------------------------------*bumpstop*[/color]
In this example, you are essentially riding on the bumpstops. You have uptravel, but no downtravel, so coming off any bumps, the wheels cannot follow the ground, and you will be 'hopping' around. This is pretty dangerous, especially on the front end; while traversing bumpy turns, your front wheels will <img src="/forums/images/graemlins/scared.gif" alt="" /> LEAVE THE GROUND <img src="/forums/images/graemlins/scared.gif" alt="" /> and the truck will want to go straight, regardless of your steering input. In this case, there is still more reduced range of travel (only 4 'travel's as opposed to 5 or 7 'travel's above) since you're almost always on the stops...
Incidentally, it is possible to keep cranking the T-bars and actually tension the suspension into the bumpstops (cirtually guaranteeing later failure, IMHO) and further reduce the uptravel, since you're preloading the T-bar not to move away from the bumpstop.

Where you fit withing these examples, I can't say, but you'll have to balance suspension travel with the amount of lift, and make your own compromise based on your own usage, always with safety in mind. Many years ago, I ran far more lift than I today feel comfortable with. Apparently I'm (getting?) old. <img src="/forums/images/graemlins/zombie.gif" alt="" />

Randii