Who makes a 525 49T rear sprocket?

[AussieAdam]

Great info on the chain.
You might find dropping one in the front works because it is equivalent about 2.6 teeth on the back.
The difference between dropping 1 on the front and adding 2 on the rear is only 5 klms an hour.
Going to a bigger sprocket on the back will shorten the wheel base and effective length of the swing arm giving you less stability and traction out of corners.
The added traction and acceleration out of and between corners might save you 1 second a lap!
This site is very useful and may help you answer some of your questions.
http://www.gearingcommander.com/