Your hardware tends to support more than the configured MTU anyway... Just for the "often forgotten overhead".
For example, a 1500 byte MTU doesn't really include the 18-byte ethernet header of 4-byte CRC tail. So 1522 is technically good.
Add more for things like 802.1Q or ISL... Or L2TPv3... Or whatever else you plan to place with..
I believe the cap is 1600 bytes if I recall correctly. Then stuff is eliminated unless jumbo frames are, or can be, enabled.
Jumbo frames may go up to 9200 bytes (again, if I recall correctly) although most seem to like 9000 as the magic number.
Bear in mind that a number of Cisco switches (and blades for the 6500) have an ASIC limitation of 8192 on the maximum size, so this may cause issues if you want to play with jumbo frames on your network.