I've been playing the fixed world for a while now, and it works very well. Thanks :)
Only thing is, I think the fishing spawners might be buggy. I clicked on one spawner and chose some bait for my Sim to fish with. He then walked up to the pond and reset (I have ErrorTrap). I tried again at another fishing spot, only to get the same result.
Going into buydebug and replacing the spawners (where possible) with identical ones removed this problem. Where I couldn't remove spawners (at the beaches), I simply placed copies of them closer to the shore.