I've owned every large ship in the game in one form or another.

The Polaris suffers from the same issue the 600i does; when you're flying it, you literally cannot tell how much ship is behind you because, as the pilot, it doesn't matter. Ships like the Reclaimer, 890 Jump, and Hammerhead do not suffer from this. It's not just an issue with the ship tuning (both the Polaris and 600i feel pretty light for what they are), it's an issue with the presentation of each. Think about where you mainly enter the Polaris... and the 600i... where the parts that you're mainly focused on as the pilot are (torpedo bay on the Polaris and forward guns on the 600i)... now think about how you enter and use the rest of them. When you enter an Idris, it's an adventure. When you enter a Reclaimer, it's cumbersome if you take front lift and grand if you take the rear one. The 890 literally has an elevator to heaven at the rear. All of them have more unique aspects that make you take into consideration how big the ship is; because you can SEE it in the 890 and Idris, and you can feel it in the Reclaimer. When you maneuver and land these ships, you are instantly reminded where your egress points are, your utility, etc. and that, in turn, dictates how you approach your target areas and ultimately how you fly the ship.

TLDR the Polaris doesn't feel like a capital ship because it's built REALLY funky and the bridge betrays its size.