I used this from the other forum for getting the angle correct, mine from the wheel to the front of the bumper is 32" unlike his 25".
Basically, measure the height from the front bumper to the ground then the distance from the wheel to the front of the bumper. Mine is 25" from wheel to front, and height was 5-5.5", used 5" for safety. So, with these figures you know the angle (for ramps) which is 10.7 degrees. But you know the front must travel at least 25", before hitting anything over 5". Each step is 13" long, and the height is 1.75".
Based on 1.75" per step, I know 2 steps =3.5", but 3 would be 5.25". So based on the height from my bumper to the ground of 5", I know that the 3rd step must be over 25" away from the 1st.
In theory top one could be shorter and if the height was 5.5" then i could climb 3 steps every 25", instead of 2. And the step could be 12.5" instead of 13". Therefore the ramps overall can be shorter. But I just played safe (ground wasn’t exactly even at measurement).
Conclude for shorter ramps: stopper = 1.5" long, top step = 14", next step = 26.5", next step = 39". Next step (could be final step if only require just over 7" in height, I found this sufficient) 51.5", if not next step is 64". Each platform has 12.5".
And the shopping list:
I bought 3 lengths of 47mm x 250mm x 4.8mtrs of sawn wood from Covers.
1st length 2 x 1380mm and 2 x 920mm
2nd length 2 x 2300mm
3rd length 2 x 1840mm and 2 x 460mm
They will cut all this for you.
That'll give you the 10 lengths you need to make the 2 ramps.
And a box of 10 x 75mm screws.
This is all assuming you have at least 5" clearance from your front spoiler to the ground. If less you'll have to re-calculate.
Hope this helps.