I'm a little late chiming in on this one... but I figure better late than never... Tuning down to drop C... I never drop lower than D on a guitar thats set up for standard... As for strings... I highly reccommend the GHS Zakk Wylde Heavy set. They make two sets for Zakk... one is made for standard and drop d... and the other is for stuff lower than that. I would suggest the heaviest set. The extra string size will help compensate for the lack of string tension when you tune way down. This will atleast help keep your neck nice and straight without allowing it to start bowing backwards. If you want to keep your guitar tuned down I would suggest doing what I did. I have two main guitars... both strats... One strat is tuned to drop D and sometimes down to C... sometimes I tune it to open D to play slide on... and its set up with GHS ZW strings... my other strat is always tuned to standard all the time... sometimes I'll half step down. So if you can afford or want to save up... just get another axe and have one for drop tunings and one for standard... it makes it easier at gigs too. Plus... the ZW strings sound a lot meaner than normal gauge strings that are tuned down.