Besides hanging low and just plain being the wrong way to go about cheap lift, a couple of other things to consider with that cheap shackle lift. Digging into the dirt would be the least of my worries.
Using longer shackles tends to only get you about half the length of the shackle in lift. For instance, 4" longer shackles would only get you about 2" lift.
The longer shackles tend to overstress and flatten out the spring, thus negating the effect of the shackle lift at some point. In the long term this leaves you no better off than when you started, and now you have to pony up the bucks for replacement springs. Lift springs would have accomplished what that guy was after on the first go around with his cheap shackle lift.
If I was buying it, I would feel that I was looking at OME lift and HD shackles right out of the shute.
The longer shackles as I understand it also change your (caster/camber, I can't remember which is which, sorry), changing your alignment and handling, which can be bad.
I am no expert, but I think the recommendations I have read for a shackle lift is to use shackles no longer than 2" than stock, and for sure get heavy duty with thick side plates, greasable bushings, and if designed properly, with a reinforcing bar welded between the side plates.