Yongnuo YN560-II flash with Panasonic G3

I have had my G3 for just over a year now. I have been intending to get an external flash for a while. I ended up getting a Yongnuo 560-II as I mainly wanted to try out off-camera "strobist" type of photography - high/low key sort of thing. I received the flash today - it is very impressive in build quality, features and operation. A couple of questions though

1. If I want to attach the flash to the G3 hotshoe it seems that the spring on it doesn't really allow the flash to mount. The Yongnuo has a nice metal hotshoe with screw lockdown. In fact I only got the flash on about 1/4 of the way - the spring on the G3 came out. It almost seemed that spring is mainly for light-weight flashes or transmitters? Is this what other people have experienced

2. The Yongnuo has a multi mode (stroboscopic). While it works if I hold the "Pilot" button on the flash, any photos either on camera or using optical trigger only have the single flash going off. Even on long exposure (say 1 sec) and say a 4Hz setting for multi it doesn't fire. Is this an issue that with the Panasonic it maybe doesn't hold the flash pin on while the shutter is open (unlike maybe say Canon or Nikon)?
Neither of the above are major issues, as really to do mainly want to use the flash to be triggered off camera. (I'm going to make a IR filter for the G3 flash to allow me to use the optical trigger without getting light from the onboard flash). It does really seem to be a solid unit - especially for the price. ( I also ordered a flash stand and white umbrella to help get me well underway).