Hi, I'm looking to have some occasional longer reach than what the Pana 100-300 can provide. I know there is no real teleconverter for m43 unfortunately, but was wondering if anyone have tried front-mounted solutions? Sony/Panasonic/Olympus all make ones that I would hope are at least decent, though with a front filter thread of 67mm, most of them are too small. Not sure if at the 300mm focal length, it could perhaps be ok to use step-down ring? Any suggestions/sample pictures would be greatly appreciated!