I don’t think you have ever used an Odyssey and don’t know what you’re talking about at all.
The Odyssey has an obvious gap between its shield and hull in the head and tail. Comparing it with Maelstrom from Diable Avionics it will be extremely obvious, and the huge gap plus the terrible turret layout often put Odyssey outranged by any capital because enemy can hit its shield at much longer range than it can to enemies. It’s almost required to use advanced optics if it wants to stand a chance, or just become a big shrike using autopulse and over extend to death. The only saving grace is the fighter bay providing assist but Xyphos perform terribly even with mod assistance so it’s better off back to long bow spam.
To sum it up, the oversized shield puts Odyssey in a terrible place, and overcharging it with 45DP (more than most capitals) not doing good enough job. If I want to hunt down small stuff, Aurora does a much better job at much cheaper price and more reliably.
Nope it's because shields have to be circular, regardless of ship shape. Other "long and skinny" ships like the Aurora and the Valkyrie also have a pretty noticeably larger shield area compared with the ship's size. The shields are typically roughly 20-50% larger than the length of the ship, and the Odyssey at 39% is higher than average but not excessively so. Some also seem to be bigger than usual for thematic reasons I believe; for example, the Paragon's shields are the same size as the Odyssey's (radius of 270), despite it being about 8% shorter; so the Paragon's shield radius should've been 243 instead of 270 proportionally speaking, to match the Odyssey's. The Aurora, despite being less than 2/3 the length of the Odyssey, has a spacing (between the shield and the front of the ship) that's around 89% that of the Odyssey, so it's actually proportionally a worse offender in this regard as well. (For both the Paragon and the Aurora, the shields are over 50% larger than the length of the ship. The Apogee as well.) It *seems* like high-tech shields are usually bigger proportionally, but this is not always the case.
Sure mods can set their shield radius to whatever they want, it's just a number in the ship file. Maybe some enterprising mod author has also tried making the shield radius smaller than parts of the ship (so that the nose and tail extend outside the bubble of the shields), who knows. Mod ships aren't a good metric for what vanilla ships "should" be though, it's the other way around -- if the Maelstrom's is noticeably smaller, then it means that the shield radius for the Maelstrom may be too small compared with other ships.
If you're complaining about having to use advanced optics, that has little to do with the shield bubble and more to do with the fact that the large turrets are closer to the center of the ship, rather than at its boundaries. Even if you reduce the shield bubble to be 20% larger than the length of the ship (matching the Atlas, for example -- which, as a freighter, makes sense thematically that the shields are barely bigger than the ship), the shields would be smaller only by around 30 units, compared with the 200 units that advanced optics provides. The Radiant for example has a shield spacing that's even larger than the Odyssey's, despite being only 78% the length, but its large weapon mounts are in the nose instead. The shield spacing (at the nose) for the Paragon is over 30% larger than that of the Odyssey, but it also has large mounts at the nose, farther away from the center of the ship. So if the Odyssey's large mounts have a lack of "reach", it has little to do with the shield size.
Edit: The Maelstrom's shield bubble is only 16% bigger than its length, which is far below what's typical for vanilla ships. Probably because it's a very long and very skinny ship, but it's up to the mod author.