Add an option (use telescope when firing), when this option is enabled, player will be able to lock the aiming distance (marker) and adjust fire as necessary for more accurate long range hits.
1. Aim as usual.
2. Lock the aim height/distance marker and switch to telescope - (Shift + Right Mouse button.)
Shift - lock the aim height/distance, to stabilize.
Right Mouse Button - telescope view, to adjust fire.
Space bar - single shot to measure the distance and see if shot hit the target.
Left Mouse Button - Fire full broadside at locked coordinate.
If test shot misses the target player must repeat the process - Release Right Mouse Button, re-position the aim height, Press Shift to lock it, press Right Mouse Button to switch back to telescope and use Space bar to fire a test shot. When test shot hits the target press Left Mouse Button to fire the full broadside.
*When you release Right Mouse Button and back to normal aim view the lock is reset.