As far as length of bolt is concerned, it depends on how un-level your floors are. In my 100 year old house, things are definitely out of plumb. Thankfully, I didn't need to alter the spikes, so I doubt you will.
If I recall, the spikes have about 1.5-1.75 inches of thread exposed before the spike.
B
If I recall, the spikes have about 1.5-1.75 inches of thread exposed before the spike.
B