Roller placement

Please take into account I have no idea what I’m doing so you will probably roll your eyes. Hopefully this will be a useful question for people starting a project though.

@patcooper kindly shared his 3D printer STL files for rollers. This prompted me to dig the various components I’d previously printed/salvaged out from the loft.

Picture is of the prototype frame design before I start bolting things together. So the question is where would be the best place for the rollers and stepper motors to go?

My thoughts are the red being rollers (these will be a bit lower so the film is flat through the gate) and the yellow being stepper motors.

Also is the fact I haven’t got a sprung tension arm going to cause issues?

Am I making some really bad school boy errors before I start bolting things together?