SOLUTION? BUILD A JIG! A circular saw is a very common tool for home owners. You can buy battery powered versions that come in kits or go for a nice corded one. This should take you about an hour if you have all the supplies.
This instructable is a follow-on to a concept presented by http://www.instructables.com/id/Cutting-plywood-the-easy-way/
Step 1: Getting Started: Supplies and Information
Circular saw (1)
Hand Drill (1)
#10 Drill Bit (1)
Countersunk 10-24 sheet metal screws (15)
10-24 nuts (15)
4x8 1/4" Hardboard
1"x1"x1/8" Aluminum Angle (Length as desired)
Step 2: Get out the saw! Cut the new base.
Step 3: Holes are a good thing!
Drill holes in the aluminum base of your saw.
I drilled 4 holes, 1 in each corner of the base.
Lay your aluminum base and mark the holes on your cut piece of hardboard. Make sure the smooth side of the hardboard is facing down.
Drill your holes to match.
OPTION 2: (Preferred)
Clamp your hardboard to your aluminum base and mate-drill the parts together. Make sure the smooth side of the hardboard is facing down.
Again, I drilled 4 holes, 1 in each corner.
Using your countersink bit, countersink each of the holes such that the 10-24 screws will set flush in the holes. You need to countersink the underside of the panel.