I haven’t found this bug being reported yet, hence the new topic.
If you expand an existing field, the game calculates the size of the existing field plus the size of the new expansion - up to a maximum size of 288 tiles. However, you can add as many such expansions as you can fit around the original field, as long as you add them all at once.
This way, you could start with a 22x5 field and add 14 expansions around it, each 5x35 in size. That gives a total field size of 2560 tiles. I haven’t tried actually constructing that, of course.
Another bug in the same vein is that you can apparently extend your expansions indefinitely into unexplored tiles, which seem not to get counted. I’ve tried it and my labourers starting clearing an insanely long field, most of which they first had to explore…
On top of this, a probably already reported bug allows the player to even finish massive fields in a reasonable amount of time: First putting down building blueprints covering almost all of the tiles you then draw a new field over. As long as it ends on free tiles, the game allows this - but also substracts the covered tiles from the total workload. When you then remove the blueprints, the workload of the field does not increase, but a full sized field will be finished after very little tilling.
I hope this helps in squashing these bugs!
