Well, here is the result of my efforts to build a cheaper routing aid for my OF1400.
I decided to use 3/8" Lexan (clear polycarbonate) for the sole plate, and 3/4" white UHMW for the fences. The plastics dealer didn't stock 3/4" lexan, and the UHMW was much cheaper and has a lower coefficient of friction. (Plus it's easier to machine!).
The project went relatively well. Here are the steps to create it:
1) Removed protective paper from top-side of 6"w x 12"l x 3/8"d lexan. Left the backing paper on the other side until all other step were completed, to prevent unnecessary scratching.
2) Etched cross-hairs in lexan using a offsite wheel-gauge. Two passes with the wheel gauge left a decent line.
3) Drilled 1 3/4" hole in centre of lexan using a hole saw on my drill press. If you are having trouble lining up centre in both axes, make sure you at least get the longitudial axes on centre. This will be the center line you use to measure offsets for the fence, so the hole should be accurately centered at least in that direction.
4) Routed the 4 slots. I set them back 1 3/4" from the ends, and routed them 2" long. I used my OF1400 on the guide rail, with 1/4" up-spiral bit. Be careful to hold the lexan down firmly with clamps, as the guide rail is not enough. The router wants to pull the workpiece in all kinds of crazy directions. ( I made some interesting grooves in my first attempt!).

5) I centered my OF 1400 on the lexan, aligning the index marks on the base with my cross-hairs on the lexan. clamped the router to the plate and turned it over. Marked the mounting plate holes with a punch.
6) removed plate from router and and drilled the holes using 1/4" bit and 3/8" countersink
now for the fences...
7) using 4"w x 11 1/2"l x 3/4"d UHMW. drilled 2 holes into sides of each fence for the cross-dowels. I set the depth stop on my drill press to prevent the holes from going all the way through the UHMW. positioned these 1 1/2" from ends and 3/8" from top. This allowed for a 1" jig bolt to grab sufficiently. I left about 1/32 of slack for the dowel when choosing my diameter of drill bit.
8) drilled 2 holes in top of each fence for the jig fixtures. I drilled these about 3/4" deep, to allow for the jig bolt to pass through the dowel.
I haven't acquired machine screws yet to fasten the router to the plate, so I haven't had a real test run yet, but the fences assembled nicely and are easy to adjust, yet hold firmly. I am relatively pleased with my result, and saved about $200 in the process!!!! ;D
I will probably ease the edges of the fences with a 1/8" roundover bit when I have it on my router next time. Also, I'd like to flame the edges of the lexan to polish them a bit. Lastly, I have to pick up a couple of center-finding rules to mount on the top of the jig. So far I have about 1 1/2 hours and less than $60 into it.
I hope this inspires others to do the same.
Cheers,
Rob