That is very good repair advice. the backing plate is a good idea. Some other suggestions: make a backing plate of fiberglass, don't use aerosil or cabosil as a filler as it is too hard and brttle. use milled fibers and/or a liteweight filler for the bog. use carbon instead of glass if you can. make sure the surrounding area is ground down enough so that, say 4-6 layers of 6oz. won't buldge up above the original contour. when glassing the outside you can strech plastic over the repair using tape as a poorman's vacumebag. that makes a smooth finish and a tight lam. Also tape of the repair area so it doesn't grow as you work.
hope this helps.