Looks like the only severe backroute you found was for L6. I may have to patch that in a future version. I'll have to find some way of preventing the player from building on that lower platform to bridge the gap. It bypasses an important part of the level. Thanks for finding that!
For the other levels, I tried to design them with multiple solutions in mind. Playing back your solutions, it looks like you found a few new paths that others haven't found yet, so that's pretty cool.
Looks like you found the main solution to L5. There's at least one other way to complete it
