After a couple of years rowing I've notice that using the phone on top of the PM5 rower monitor with the provided phone holder I've been developing the tendency to arch the neck while rowing (especially on the initial "catch" position). This has led to having neck pains in the cervical spine area. The newer models have remedied this problem with the holder that is located below the monitor with a new arm completely redesigned. This holder is integrated to the new design of the arm and is also available to purchase (the arm with the holder) and replace it for older models, but it's actually quite an expensive upgrade for what it provides. 

So, here's my take on the problem, I tried to find a quick and simple solution that is easy to print and install in no time. You can adjust the height position along the arm to a certain point and also the angle of your mobile device.

I hope that if you have the same problem with your rower, that you try this out and then let me know how it goes.

I print it using Prusament Galaxy Black PLA and so far it's been great. I'm sure PETG would also do the job quite well.

And if you ever need to make an adjustment due to your mobile size not fitting, the step file is provided and is easy to modify.

Happy printing!