Aw I was looking forward to making one of these. That's okay
Quote: "I think there's no reason not to use them (i.e. there's no disadvantages that I know of) and if you crash the props are far less likely to break. I didn't get any because my motors came with normal threaded shafts with nuts. In other words, if it comes with prop savers, use them. I wouldn't worry about it that much"
I've read a lot of stories across the web of prop savers breaking mid flight and becoming a safety hazard

They also increase vibration. It's possible a lot of angular moment could pop the props right off. I'm uneasy about the idea of lifting the whole quad with what are essentially rubber bands

but of course I've never used them so I couldn't really know!
Also it seems that all 4.3 pitch props are slow fly props? That essentially rules out the motors I listed in the middle (the 820g thrust ones) back on the posting competition because I believe slow fly props reduce agility
Quote: "BUT, I had an idea. Instead of trying to make the flight controller myself... I just buy one! "But then you need a traditional transmitter, silly." No, I'll control it with my Arduino!"
Why do you need the KK2.1.5? There's already open source arduino projects available for quadcopters.
Quote: "Im not sure what flight controller I want to use myself. "
In the reasonable price range the best controller is the Naze32. I'm sure there are specific features that might make someone perfer the cc3d or kk2.1.5, but in general the Naze32 is the best choice

Some people feel its too complicated to setup, but I'm confident essentially anyone on this website will have no trouble with it. Some people are intimidated by the command line feature, but it's hardly complicated
Edit: My frame showed up while I was typing this