Hi Tyler,
I would personally be doing what someone has obviously done on the red one - get an angle grinder and take a bit off the tensioner
Attached Images
Victa tensioner.JPG
This looks very obvious but will only work if the cable is long enough for the tensioner to move back
As stated back to Tyler - I am pretty sure whoever did this - and we're assuming this was 'by design' didn't really know or achieve what was desired. As the tensioner arm rest against a raised area of the chassis, with the spring pulling it back to here. The idler pulley is of a size where it will almost hit the raised area IF you go removed part of the arm.
And this is aside to the actual reason it's assumed they did this - as it still won't be able to add any more tension to a new M36 belt - as stated I literally broke the steel cable on one by trying to add more tension - the belt is incredibly tight and based on everything I've seen about belts, far too much so.
So my gut feel is that was a 'bodge' effort that achieved nothing - the only variables that can change and affect things are either the pulley sizes, pulley locations (which won't change) or the belt size - the latter being the most easily changed one. Anwyay it won't be solved today.