Backplates fit different polishers?

[dseg]

I have a GG6 with a 6" backplate and 6.5" pads.
Will this fit a MT300 or do I need to buy a new backplate since it is a different brand?

Also, I see people often buy the 5" backplates for the MT300 and 5" pads. Is there a reason they don't buy pads bigger than the backplate?

[ski2]

Standard DAs like the Griots, PC, Harbor Frieght, Megs G110 and the MT300 all use a standard DA backing plate that is available in different sizes--3", 3.5", 5" and 6" from different manufactures. 5" backing plates with 5" or 5.5" pads make the DA more effective as there is less mass for the motor to spin and the smaller pads are easier to use on curved panels. Most 5" backing plates are actually 4 7/8" so you can use 5" pads or 5.5" pads.

If you have not seen this--a list of articles and videos by Mike Phillips that can be very helpful answering basic questions--http://www.autogeekonline.net/forum/ask-expert-featuring-mike-phillips/23722-car-detailing-articles-mike-phillips.html