I am not sure about the first question; but as for what the size for a tour should be it depends - how many pages? are the pages setup to load in a way that keeps the surfers attention, etc.. Basically a good way to check, (if you have the abiltiy to) is load your site thru a dial up modem and ask yourself "would i stick around for this to load if i was waitin to get my rocks off?"
hope that helps - and i hope ya get the answer to the first question as i'd like to know aswell.
