In an upcoming firmware update, RepOne Sensor will use 3D positioning to account for lateral travel, so the position of the device on the floor doesn't impact metrics accuracy. Extreme angles (approaching 90 degrees between the tether and it's typical neutral position) will still add error as they are outside of the "cone" of 3D space the device can register, but it's typically very obvious if the unit is in that odd of a position.
A rule of thumb is for every 18" of distance the sensor is from being directly under the bar, you lose approximately 10% accuracy on your readings.
This has less of an impact on your data if you always keep your sensor in the same place, and you always unrack to the same exact position. But data accuracy is of more importance if you're trying to compare against others, or if your setup varies between sessions.
Tether angle also has an impact on tether maintenance. In order to make sure your the Tether on RepOne Sensor stays intact for a long time, avoid pulling at an angle that has the tether rub against the small eyelet that makes up the opening in the outer housing, through which the tether travels. This can fray the nylon coating. The more extreme angle reps are pulled, the greater the wear potential.
To keep your nylon coating in good shape, you can use something like 303 Aerospace Protectant. Spray a paper towel, pull your tether all the way out, and gently squeeze the base of the tether with the sprayed paper towel while it retracts all the way back into the device. This should be done once every month, or when you feel the tether becoming more 'tacky' or dry.