Dunno what else to suggest but yep, reducing the ride height will bring the CofG closer to the ground making it less likely to topple, and upping the preload will make it less likely to ground out.
The only other thing is to fit a longer stand leg, take yours off and trot along to an auto jumble (your local Honda dealer should do) and see if they've got something a half-inch longer. What about carrying a piece of wood to put under it whenever you stop, or weld a thick piece of plate onto the foot of it?
