The best place to insert an inline amp is near the bottom of a larger circular trash can ......... LOL!
Amps should only be used as a last resort. For long cable runs, consider a higher grade coax cable instead of an amp. Upgraded coax cable will not introduce noise, amps will introduce noise and usually will degrade the Signal Quality.
If you must install an amp, it is best to install near the LNBF. Your insertion between the motor and LNBF would be appropriate.
Do this experiment: Prior to inserting the amp, record the Signal Quality on a Strong TP and a Weak TP. Insert the amp. Compare the Signal Quality readings. Please share your findings.