Personally I would never go under a car - on axle stands or ramps - without a secondary support in case of failure. I always worry about weld failure etc.
One of my best car related purchases was a 3.6mx250mmx125mm sleeper which was cut into 400mm lengths. This gives enough pieces to securely support a car.
I also purchased a 6.0m length of 220mmx50mm construction timber board and cut this into 400mm and 800mm lengths to use on top of the sleepers to obtain the correct height.
https://buildingshop.co.uk/product/n...EaAoLsEALw_wcB
or
https://www.clarkesofwalsham.co.uk/o...EaAngBEALw_wcB
plus
https://www.builderdepot.co.uk/47mm-...-page-product1