Thanks for feedback Impaler
I know the issue about scale, and them being bit unreadable as it is just plain sideview. I started sketching those as intention to do icons, but they turned too complicated. But still being quite small drawings and directly from sideview, they lack details to bring the impression of size and shape. But dont worry, I'll redraw and design them clearer. I got quite excited about those winged designs of scout and missilecruiser, I might redo whole shipline to be based on that kind of structure.
Just in case you're interested, scout h=30m, missile cruiser h=70m, battleship h=150m, titan h= 450m, you can see some common details, as the 3 fighterbays at the side of battleship and then similar bays at titan. And battleship has one huge gun (cannon radius ~ 15m) installed at the middle of upperhull, the titan has 3 of those in rotetable wing at it's side.
Well, not only engines are heavily armored, everything is

only scanners, ecm/eccms, weapons and things with heavy heat-output are left open. Actually engines arent so protected as they are complitely open when approached from behind.
Heavy hiding of engines was general desing-decision to keep the feel of the line specified along with heavy circular armoring, vertical direction of ships and those animeish radars/ecm/eccms towers that make these ship look like are made by same race.
About second picture, I realised once I had done inking how much those huge missile launchers bring down the size - needs redesigning :/ but on positive side, you get the idea of right size if you look at the bridge and the tiny figure barely seeable behind controls - and then think about the size of the bombs those launchers are holding

This multi-use-cutie can take down fighters with those fast cannons and capital ships with heavy bombs/torpedos.
Much talk for few sketches, that's good. Now I'll have to call my secretary to book me some time for redrawing these
And That Guy, can't wait to see your new renderings

Have you thought orbitals yet?
Cheers