from one Marylander to another, glad you found us. Congrats on your new camper. I have one of those large levels on the front of my camper and it works pretty good, but reaction is a little slow so I have to give it a little time to settle. With out getting out of the truck I can tell which side needs a lift, so I rate it on a scale of 1-10.....a"9".
As far as the plastic blacks, in my book they are so,so the good things is that they are light in weight, I do use them but I place wood under them so that they do not work there way into the ground, they are not solid on the bottom and I also found that the higher they are the more flex there is and become loose between the foot of the jack and the top plastic block. Give it a try they just might work for you.....
others seem to have good luck with them.