I just wanted to thank DroneDeploy for the work and collaboration done to improve the linear flight app. I cross-link to a thread regarding the ability to choose any waypoint for the start in order to greatly increase the efficiency and get this mode nailed down. 
https://forum.dronedeploy.com/t/adjustable-starting-waypoint/12640/6
This is the survey for a tributary drainage channel that we are improving. Tough job and allot of muck. Nailed the flight plan to cover the specific area.
I’ve requested to allow more than 6 paths, I fly between 80 to 120 feet altitude and sometimes I need more paths to get the data (photos) I need.
You can wrap the line back on itself. Like a U… You just have to size the turn so that you maintain the approximate same sidelap in the middle.
Yeah I know I can double up like your photo.
That would work on streets, which I have done before. But if I could just add 2 more paths would be a lot easier on planning.
Rivers is just a pain with all the twisting and switch backs.
As a developer, I wouldn’t have limited it to 6, I would have made it at least a 10.
I pretty much agree with you which is why I gave you a like. I don’t think there should be a limit to how many lanes you can use. Question is why do you try to follow a subject like that so accurately when you could go from major pi to pi and probably increase the efficiency of your flight? I’m working on a 3-mile hike and bike trail the parallels a major creek in our area and don’t have any trouble configuring through switchbacks and capturing offshoots.
Streets and paths are pretty easy to setup and fly. Rivers can change widths throughout and setting a single centerline (ok eyeballing it, lol) flight path with x side lines to either side just makes it easier to setup.
Your photo below is a excellent work around to the issue. I agree unlimited side lines is what I told our DD Rep but if we can at least get 10 lines vs 6 would probably take care of 90% of the flights.