[quote=@Legion02]
[@Willy Vereb] It's a can of worms and I'm not entirely against it but maybe we could use volume or tonnage instead of size? My ships are rarely of the long cigar shapes so that wouldn't really be fair.

Alternatively, if nobody specifies the sizes then we can just adhere to the hierarchy and people whose ships are "treaty breaking" would have to specify so. (Or, when skirting, say what they skirt.) That way we can leave the technicallities behind while maintaining a semblance of powerlevels. As I assume most ships would also have a specified weakness.
[/quote]I explicitly stated that non-longitudal ship designs or similar shapes can work with smaller dimensions. I would rather not specify volume because that's on the "too thinky" side. I can go into [b]*WAY*[/b] more detail but I feel anything but a simplistic list would be counter-intuitive. 
I CAN give you a diameter list for saucer and spheroid/cube ships which follows this scheme if you want, though. Would that suffice?

[b]Spherical/Cuboid Ship Chart:[/b]
- Hyperdread: >2000m
- Dreadnought: 800-2000m
- Battleship/Battlecruiser: 400-1000m
- Cruiser: <500m
Others should follow a roughly similar scheme of decrease. In case of strike craft you just have to be conscious of making your fighters noticeably smaller than the average.

[b]Saucer/Plateoid Ship Chart:[/b]
- Hyperdread: >2500m
- Dreadnought: 1000-2500m
- Battleship/Battlecruiser: 400-1000m
- Cruiser: <500m
Again, you can figure out the rest according to this. As for strike craft you don't even neccessarily need to reduce their dimensions. You still use the base plane form for both, in case of flying saucers the "wings" are just circular.

Hope this could help.

EDIT: If you plan to use Star Trek Federation style saucer-longitudal mix kind of warships then those could be either follow the saucer or the longitudal ship size limits. Either works, really. At times there are as much as two orders of magnitude difference between ships in the same class here in terms of volume and that's fine. Good enough for what is a space opera here.