1. Very fast shutter speed to ensure crisp frames for twixtor to interprete before and after frames and then create the frames between, although you may have to do some post work to prevent warping on edges between stationary background and the moving subject, assuming the camera is locked off. I have not used twixtor for a while, so the app may have solved some of the issues I refer to. Shutter speed requred will depend on the motion speed of the subject moving. Something to test before the shoot and light accordingly.
2. Lighting, you may need some, and if so, some may cause flicker at or around 1/100 or above. Depends on the lighting source. Power is a 50 hertz pulse where I live, and 1/100 is the highest I can go to avoid flicker with most domestic and industrial light sources. Domestic LED, I found up to 1/400 did not flicker from some light sources in the building carpark where I live. Some shutter rates will flicker, depending on the math, so some of the inbetween shutter speeds may flicker as you increase, and others will be ok. If you have lights or are hiring some, you may need to investigate which to use at the shutter speed desired so as to avoid flicker in your footage. If outside in the daylight, you should be fine at a very high shutter speed. Just check the effect it is having on the image/footage with some tests and patch you use before the shoot, and review the footage on a monitor in post.

I know you asked about a patch for the GH2 and my suggestions above may be common knowledge to you. I shoot 720p50, so I can't comment on 60p patch results and stability, as they are going to be different to 50p patch results.

@Bania, last year I was shooting 720p50 footage of RC Drift Car sessions where I also participated. When I started recording in early 2012, I installed Driftwood Quantum v6 Beta shooting indoors at night and could not go above 1/100 shutter due to flicker from the industrial lighting source. No twixtor, just 720p50 played back at 50% speed in a 25p timeline for smooth slow motion shots.

A few months later, I installed Driftwood Quantum X v4d Orion 'Dark Matter' V3.
I shot this a few months ago at 720p50 at 1/400 daylight, played at normal speed in 25p timeline, AE stabilisation scaled the handheld footage, so softer than normal. Same footage, 720p50 at 1/400 daylight, played at 50% speed in 25p timeline for smooth slow motion, scaled up as a result of AE warp stabilser.

I remained with the Quantum X patch until a week ago, testing Low Rider v1.0 for 24p acquisition. The above samples may not be relevant to your proposed shoot because I never applied twixtor. Twixtor applied to the indoor footage shot at 1/100 would not be very good, because there is too much motion blur as the cars pass, and that would not be ideal to create inbetween frames by twixtor. Daylight allowed me to record 1/400 and above, better for twixtor. Indoor shoot with lights, use the right ones for high shutter speed recording! I have not yet tested Low Rider at 720p50. My old Quantum settings worked for me so I never changed, however, a lot of patches were created since Quantum, so you may want to ask @driftwood or other settings creators and users which of the patches would be best for your higher shutter speed 720p50 recording. Good luck.