Try to put my weight on the heels to inflate less

You walk on but, to try to limit how much the plug inflates, you put as much of your weight on the heel of the shoe as you can.

It works... sort of. Because of the wedge shape of the shoe, it's much harder on your legs and back, and the pumps still move a little air with each step, but you think it's less than it was when you took normal steps.
You can only hope it's enough however, and as you get deeper into the forest, you begin to worry that it might not be. You have no idea how far you need to go.

After a while, you pass a first and then a second mile-marker, telling you you've gone over a mile in this thing and it's already starting to get big. It presses outward against your inner walls filling you as much as any penis and then some. Oddly, because the inflation is centered deeper within you it isn't as bad as you might have worried. It's pressing but not pulling open the entrance the way a dildo would.

It's not so bad. The way the base tickles the entrance while the inner bulb presses out, filling what feels like every nook and cranny within you, is only enhanced my the motion as you take each step. It all rubs the slick wetness of your sex in a way that is surprisingly wonderful.