With all the complaints I've had regarding Samsung and their mounting holes, I've never found one where the top and bottom had different bolt sizes, except in a couple models that required the hockey puck adapters as previously mentioned. If the panel has a big step out towards the bottom, then there should be the adapter pieces. Given you are working with an F series, I assume this is a TV that someone has either moved or just finally decided to mount and those adapters are now missing.