Collin,
well, a 250 mm circular saw from Makita is a model I am unfamiliar with - how old is the thing?
I totally agree that the stamped metal bases that come with the saws inported into N. America suck. Again, it is a case in which the good stuff is not brought over here. the quality saws have a stiff aluminum case base that is much better.
Case in point: Hitachi:
Note the cheap metal stamped base on the saw at the left, and the high quality bases on the saws to the right.
Case in Point: Makita:
This saw is available in 380 mm (about 15") and 415 mm (about 16.33") sizes. Again, note the base.
I'd like to see a picture of your saw.
Chris