I understand that rental cars can now use Saddle Road (not the case when we were last on the Big Island back in Sept 2010). Do we need a 4wheel drive rental to get up to the Visitors Center of Mauna Kea or is the road now suitable for standard rental cars? We would love to go as that is one of the few things we couldn't fit in last time. If not, which tour company do you recommend? We arrive tomorrow and will be on the island for 10days and so hopefully will be able to get up there weather permitting.