After my new back seat is made I would like to skip the side pieces that are currently between the front and rear seats. But there is an access hole there that is about 4"x6". I found some cupholder inserts that I could use by cutting the holes larger and to shape. But I don't know the best way to deal with the "ridge" just under the current hole when mounting the inserts.

Any ideas to make it look good?

Slowly file on the new insert to make it fit. Or just cutoff the bottom lip on the insert and mate it flush against the ridge, then use a white 4200 to seal it.

I'd do all your cutting at the top of the opening so that the insert will slide in and rest right on top of that ledge, w/o cutting the insert bottom lip itself. Once you start cutting that insert lip, it'll have a gap since that lip isn't solid?????

The gap should be covered by the lip and the sealant

What they said

Hey guys the existing hole is only about 4x6" and I will have to make it bigger(7" tall x 10" wide I believe). So, there is no getting around cutting over the lip which is what I am trying to figure out. There will be a gap on the top part above the lip.

Build a little frame out of plastic,( Coosa, KOA, Azek, whatever) that has a face that will be flush with the ridge. Dont be skeeered!!!!!

Gotcha, now I remember how high up that lip is. I would get some starboard, and have it machined(or do it yourself carefully) to make up the gap on the upper portion.

Starboard, coosa, koa, c'mon speak English guys!

Just kidding I will google these materials to see what they are.