Not all channels in the 5 GHz band are "equal" in that some are under DFS restrictions and you can't "start" a 40, 80, or 160 MHz bandwidth channel "anywhere". With DFS, you'll be pushed out of the DFS region as soon as there is a detection of radar in operation (which could be many miles away from you). I don't recall exactly how hostapd numbers wider channels, but you may have to play a bit with the "base" channel number.
The article linked by @jeff explains the channel allocation (for the USA) really well. It ends up that there are two valid non-DFS 80 MHz channels: 42 and 155. 42 covers up the entire lower non-DFS band, and 155 uses the higher non-DFS band except for channel 165, where 20 MHz operation is possible.