Just something I've been working on

[Syrus]

First of all, I got to say I think it looks good, very detailed and mostly not "unrealistic".

But:
The front needs a little change, those antennas - what purpose do they serve?
It'd be a bit too dangerous to have them there as they would be damaged very quickly. Also they look a bit unfitting anyway. Next thing, while the rest of the ship has many details, the front surface is kept very flat without anything on it, maybe add some details here? But as you said, it's already very poly-heavy. So, only those antennas which stick out a bit.

In the back, those long flat shapes behind the protection armor... I think they'd be burned by the engines. But even if that doesn't matter, they aren't necessary. In flight the enginetrails would take up that space.

Bottom details - Nah, good texturing can make that happen. You can make up the lack of details in that scale by having very good texturing over it. Might not be 100% like having more details, but it gives some variation.

Thin - it is indeed thin, as you said, you want to make it like you want to, but I wanted to comment on your size comparision: It doesn't matter how BIG a ship is, if it's very thin compared to it's length / width it'll break much more easily. It requires stronger materials or technology to strengthen the hull integrity. Mhh...but yeah, it'd be to thin for my taste as well.

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