P3Steel Y-Axis Adjustable Belt Tensioner

This is a remix of MattyVee's brilliantly simple design. After having the tensioner in use on my Prusa MK3 for some time I've decided that it would be a great addition to my P3Steel as well. All solutions I've found for that printer were either clunky, wobbly or hard to get to (two screws under the heated bed etc).

There's one little problem with the P3Steel and this design: the two horizontal screws holding the Y-Idler come out right under the inner wheel holders and - and this is the bigger