I restored an old used RC12L that had a graphite chassis about a year and a half ago. To freshen up the well worn chassis plate, and keep it from flaking and splintering apart I knew I needed put some sort of coating on the bottom. I used gap filling CA glue, wax paper, and two pieces of glass that were just bigger than the chassis.
-I laid one piece of glass on a table.
-Then a layer of waxpaper (larger than the chassis of course) on top of the glass. Ensure the wax side is facing up.
-Then the chassis, top side down, on top of the wax paper.
-THen ooze the CA glue onto the bottom of the chassis over the whole chassis. Don't over do it, but ensure in the end you have complete coverage over the whole bottom of hte chassis.
-THen another piece of wax paper, wax side down onto the glue.
-THen the second piece of glass on top of the second piece of wax paper.
-Finally, place a tall stack of books, weights, or something else pretty heavy on top of this sandwich you just created.
It will take about a week to fully cure, but when it does, all of the damage will be nicely filled in, and the bottom of your chassis will look almost new. You will probably need to trim any excess glues that squeegied out, and counter sink the holes agian, but in all it doesn't take much time to prepare, and the results are very good. I've been very happy with how mine came out.