I probably did make a mistake in where each module is, yes. But that's what I have. I saw no need to have any more than 1 prospector limpet, since I'd only use one at a time. 1 (whatever class, can't remember) prospector limpet, and two 3B collector controllers for 4 limpets, a refinery (4 something), and the rest cargo. Seeing as this was only a stater/temp setup, I didn't want to spend the few credits I had (started a new game a few days ago), on top-rated equipment. My requirements were: most limpets (collector) for least credits, and most bins for least credits.
If it's credits, use D-rated collectors. They last much longer than B rated and they're cheaper. You only use B-rated when range is your main concern, such as scavenging.
Always use A rated prospectors. They give more fragments per roid, plus they last longer and have good range.
If you want a budget miner, try this Keelback.