Sloping driveway parking

One thing you are going to have to watch when you need to go uo that much is the height of the front air dam on your unit. Take a board and place it in front of your front wheel. Now raise the front end up until you hit any part of the front of your vehicle. Mark the board where it touches the vehicle and measure the height at that point. Subtract an inch from the height as when you back down the ramp and hit bottom the suspension will contract and you don't want to tear that front air dam off. Measure the length of board to your mark in feet. Assuming your height minus an inch is 6" and the distance from the front tire to the mark is 2 feet. Your ramp can only go up 3" per foot of ramp. For 12" of lift you would need a minimum of 4 feet of ramp.
You may have a hard time finding an over the counter solution that long.