This is a proggress viable setup that i personally used when breaking into C2. Im using the "The Ramparts" map as it shares the same layout with "Ramparts Siege" with the addition of 1 optional objective to the right side of the map.
The build is pretty much the same as well with the top right lane moved slightly back so the bonus gets destroyed and they can cover the extra lane aswell. I needed some more defenses to cover it and as such i opted to remove the "Skyguard Tower", This does mean that you have to apply allot of personal focus to the fliers(especially the kobolts), and removed 1 baricade/PDT from top lane leaving 1 each to cover it.
The general strat i use for pretty much any map is 2PDT per lane, 2Flamethrowers per lane (3 if DU allows or more is needed), 1 Spike Blockade per lane and a Skyguard tower where ever needed.
Whenever possible i place all the "Flamethrowers" and the "PDTs" on ledges out of the main path of the enemies.
This build I find a lot harder than any of the other C2 maps. This was the last one in completed succesfully only due the fact i had a fair amount of C2 gear from previous maps.