I have this rear derailleur with a 28t-14t freewheel, and a 36t chainring in the front. I plan on using this freewheel till it wears out (this is my beater/grocery getter), but could this derailleur handle a wider range? Like 30T-12T? I run out of gears going up and down hills, and it also makes any head or tail wind less efficient. Is Shimano being overzealous with their derailleur capacity? Or would it be a disaster to go to a wider freewheel range? I don't really want to put a front derailleur on the bike.