I had a very similar setup until tonight. I just got a Veritas steel table top and the Veritas router fence. I just finished installing the top. Woaw, what a difference with the Veritas fence. I decided not to fully enclosed my LV table top because of the fence clamps that attach on the side of the table.
You will appreciate your router extension. Nice job.
Also have one in my saw, but used a Jessum router plate. I used 3/4" melamine with 1/2" MDF under it to prevent sagging. I made a fence that slides in the T-Tracks of he R4512 fence. Who needs micro adjustment when you have a tablesaw fence!
I built this with 3/4 melamine , my old boss gave me. Its pretty great stuff, dead flat. The insert is from rockler.com, and the frued router is a combo I picked up from home depot for $99.99 it sales for close to 199.99 other places. I cut the melamine to size and added poplar under for support. Once I got it in place I clamp it down flat to the table with 2×4's, then drilled through the provided mounting holes with a 1/4 drill bit and used 3" bolts and washers to secure it.