Hi!
First of all, sorry for the delay in replying, I’ve been a bit disconnected for a few months and I haven’t seen the message until today.
What you are commenting about using larger motors in joints 2 and 3, may be a bit of a problem. The Art1Body part is designed for 34mm geared motors to fit tight. In fact, the walls are narrower than I would like to allow the motor to fit in that part.
If your geared motors are larger they may not fit in the space where the motors should go.
My recommendation, if you can’t/want to use the recommended motors, is to print the Art1Body part first and test to see if your motors will fit.
In the event that they don’t fit, you would have to redesign the part, enlarging it to make room for the motors. It’s not impossible, but it involves a considerable amount of work, as you would have to redesign some of the other robot parts accordingly.
Regarding the firmware configuration, if the motors without the gearbox are 200steps/rev (which is usually standard) and the gearbox is 5:1 you would not have to make any changes to the firmware because the parameters would be the same as with the recommended motors.
Finally, regarding the power supply, I always recommend a 12V and no less than 8A, ideally 10A.
Hope it helps!