Do like playing with evolution in restricted enviroments myself. Normally gravity works great. I've also done bots with no movement code at all in a brownian enviroment. Every so often you'll have a trait evolves thats bad to a group overall, but the spread will be naturally limited.
Had some good effects with walls when we had them. One species developed one feeding method, while the other found a completly different method.
As to DNA lengths, generally the first things bots mutate effectively are deletions or inactivations. You'd be surprised at how mnay things we give our bots to be "better" seem to be the first to drop off.
Whereas insertions of new matterial is quite dangerous, since it could really be anything. So maybe there's a selective pressure against the insertion of new code, which is why your bots aren't growing in DNA length.
I agree with this completly. They also seem to like playing around with the gene structure lately to accomplish inactivations quicker.
Some of what we think would help the bots actually restricts them in an evolving enviroment. They'll be adapting to evolving family, enemies, and the enviroment; what we generally code for is just efficency and fighting enemies in a species/species combat enviroment. There's also a question of fault tolerance. For instance it's better when mutating to either tie permanently at birth or not tie at all. A birth-tie will always naturally deltie itself a regular tie can not be expected to always do the same with mutations involved.
On another note
Is that how you manage to afford to cruise around so much? I'm onboard a sub and it's insanely expensive just to get us from one port to another.