In case anyone stumbles upon this thread looking for answers to these same question, I can now answer them, because I installed the runcam split min 2 into my leader 120. Space is indeed extremely tight. With the stock canopy, I don't think there's any possible way to fit the split mini 1 inside. I had to switch the stock nylon standoffs to the slightly smaller brass ones that come with the camera. Even then, the top of the canopy frame ever so slightly makes contact with the edge of the split mini 2's circuit board, so I covered the top with tape to prevent any shorts just in case. The camera itself also has to be wedged in there in a rather jury-rigged manner, so don't plan on being able to adjust the angle on while out in the field. The holes where the screws would mount the camera in aren't able to align with the corresponding holes on the canopy, but you can put screws it in anyway as a means to keep it from sliding out entirely, as you can see in the photo. Otherwise it's basically held in by pressure, though it feels pretty snug. It might be worth investing in a larger stock canopy at some point.

I also purchased a runcam tx200u transmitter to go with it, and with the use of double-sided tape, it just barely fits onto the back of the camera. You could theoretically mount it on top as well, but I don't want to leave it too exposed to debris.

The video looks great! Lightyears beyond the stock camera. It even has a tiny microphone, which sounds like crap obviously but is still a neat feature. I haven't had time to test it in a real flight yet, but I powered it up inside my apartment and everything seems to be OK so far. It will probably cut my flight time by a minute or so, but that's worth it for the upgrade in video quality. And as far as latency goes, the people on here complaining must have god-like reflexes to notice. I'm by no means an ace racer and just like to fly around lazily, so I don't think it's going to be an issue for me personally. Can't wait to take it for a spin in the park!