and noticed many Class-B RV were using various blocks or
ramps in an effort to get the RV level.
Here are a few examples.
None of the above are what I would consider acceptable. They all are too narrow or the tire is not properly centered.
The ENTIRE tread contact patch should be supported. On the left above you can see the contact patch and the size board I use.
Too narrow or with part of the tread hanging off one side can put extra stress on the belt edge and result in the initiation of microscopic cracks that could grow into a Belt Separation.
If you have some of the plastic supports you first need to confirm they are wider than your tire. You also need to pay attention and be centered side to side and fore /aft on the support.