I can't specifically note for your 1900 but I installed a set on my 13' rib and the instructions said to start in the middle position. WOW what a difference and never needed any adjustment. You probably won't "need" any adjustments but may want to tune them. I would say try them in the recommended position then next time out move them and see if you notice anything. I doubt they will have so much effect that it will be inoperable. If you can reach them from on board you can probably adjust them at anchor. Only thing you have to worry about is dropping parts. Maybe beach the boat so its not too deep if you do drop something and bring a magnet.
I have the trailer brackets that allow me to flip up or else they get compressed on the trailer bunks. So keep that in mind if you need them and interfere with your trailer. They are pretty cheap. Beside beaching, the brackets are also useful if its bad weather in a following sea. You may want to flip them up to keep the bow up.
They really are set and forget and have worked great for me for 2 years now and we put tons of miles on it.