I have a friend that knows a bit about coding and crap and he made me a bot for rusty caps, and only rusty caps, it drops everything else automatically.
Items you need: Composite Fishing Rod, Rogue Rig, and Fishing Gloves
I have compiled a ZIP of the bot and it's coding, so it might come in handy for you.
(You need gloves for +1 skill and also so it don't drop caps. You can use any other type of gloves but I recommend fishing gloves because that is what you'll be doing..)
OK, to begin, start off by making a macro on the ALT+1 slot and insert this:
/hide
/chatmode party (for reasons that if it accidently messes up, it sends to party instead of say)
/fish
This should do for now, log out, and start the bot, log back in and you're set.
File:
http://dirtystinkinapes.fragism.com/bot.txt (Right Click, Save as, Rename to bot.zip, and open.)
Extract to ANY folder, anywhere. Run POL and then start the Fishing Bot.exe