Start by having a look at this.
https://www.mcmaster.com/chain-tensioners
You should see that the manufacturers do not make pedestals. Also you will not find single pedestals, there is no substantial resistance to bending or tracking, and there is lot of force involved. Do not assume that because you saw one on line like yours that some garage guy made that it's the way to go. If it was the industrial manufacturers would make them that way.
Now lets get into using spring travel, a spring system will bounce. This will in short order break your pedestal tensioner. Elastomers work best as they self dampen.
Now that it's been mentioned your design with the bottom pivot is bad. A look at any Softail is a good example. Again just because some back yard guy did it doesn't make it the way to go.
Altering your design to put the pivot in or near alignment with the sprockets, would rid you of the need for a tensioner.
Tensioners are not usually on the driven section, unless they are solid and don't actively tension.