by fredderf
for the first part that is up to you. if you were wanting to base them any organic shape will work http://corseceng.com/omni-stand/omni-stand-asteroid-bases/ or you can make your own like i was planing on or you can just put it on the table with no base and go like that.As for the second part, in my little view of how the universe works id say yes count both the asteroid and the base as possible blocking LOS or causing collisions since the asteroid probably pitching and spinning. so if a smaller asteroid is on a larger base that represent that it is spinning madly and that base represents the danger zone or a asteroid that is to large for it base and leaves only a little the the counter exposed would not be spinning as much.
Hope this helps.